An Introduction To Electrical Science 1st Edition By Adrian Waygood TEST BANK

(C) a conductor.

(D) an insulator.

Answer: (B) a compound.

6

An atom's positively-charged sub-particles are called (A) neutrons.

(B) protons.

(C) electrons.

(D) quanta.

Answer: (B) protons.

7

An atom's negatively-charged sub-particles are called (A) neutrons.

(B) protons.

(C) electrons.

(D) quanta.

Answer: (C) electrons.

8

An atomic sub-particle that carries no electrical charge is called a (A) proton.

(B) neutron.

(C) quantum.

Answer: (B) neutron.

9

An universal law that applies to electrical charges states that (A) like charges attract.

(B) unlike charges attract.

(C) like charges neutralise.

(D) unlike charges neutralise.

Answer: (B) unlike charges attract.

10 The outermost shell of an atom is called its (A) k' shell.

(B) l' shell.

(C) m' shell.

(D) valence shell'.

Answer: (D) valence shell'.

11 The chemical and electrical properties of an atom is determined by its

(A) k' shell.

(B) l' shell.

(C) m' shell.

(D) valence shell'.

Answer: (D) valence shell'.

12 An electrically-charged atom is termed (A) an 'ion'.

(B) a 'positive ion'.

(C) a 'negative ion'.

(D) a 'positron'.

Answer: (A) an 'ion'.

13 A 'positive ion' is an atom with (A) more electrons than protons.

(B) more protons than neutrons.

(C) more protons than electrons.

(D) more electrons than neutrons.

Answer: (C) more protons than electrons.

14 A 'positive ion' will tend to attract (A) protons.

(B) electrons.

(C) neutrons.

(D) other atoms.

Answer: (B) electrons.

15 A 'free electron' is an electron released from an atom's (A) k' shell.

(B) l' shell.

(C) m' shell.

(D) valence' shell Answer: (D) valence' shell 16 If the outer shell of an atom is less than half full, it will tend to (A) attract free electrons.

(B) lose electrons.

(C) be electrically negative.

(D) be electrically positive.

Answer: (B) lose electrons.

17 If the outer shell of an atom is more than half full, it will tend to (A) attract free electrons.

(B) lose electrons.

(C) be electrically negative.

(D) be electrically positive.

Answer: (A) attract free electrons.

18 In metals, an electric current is (A) a rapid drift of electrons from negative to positive.

(B) a rapid drift of electrons from positive to negative.

(C) an extremely-slow drift of electrons from negative to positive.

(D) an extremely-slow drift of electrons from positive to negative.

Answer: (C) an extremely-slow drift of electrons from negative to positive.

19 A general definition of electric current is (A) a drift of free electrons in a conductor.

(B) a drift of electric charges in a conductor.

(C) a drift of electrons from positive to negative.

(D) a drift of ions from positive to negative.

Answer: (B) a drift of electric charges in a conductor.

20 Silver, copper,and aluminium are examples of practical (A) semiconductors.

(B) conductors.

(C) insulators.

(D) compounds.

Answer: (B) conductors.

21 Ceramics, glass, and plastics are examples of practical (A) semiconductors.

(B) conductors.

(C) insulators.

(D) compounds.

Answer: (C) insulators.

22 An electrical conductor is normally electrically (A) positive.

(B) negative.

(C) positive or negative.

(D) neutral.

Answer: (D) neutral.

23 A 'displacement current' is (A) a flow of electrons within an insulator.

(B) a flow of charges within an insulator.

(C) a distortion of the electron orbits within an insulator.

(D) another term for 'leakage current'.

Answer: (C) a distortion of the electron orbits within an insulator.

24 Conventional current' is (A) a flow of positive charges in a conductor.

(B) a flow of ions in a liquid conductor.

(C) the result of an error by an early scientist.

(D) no longer used these days.

Answer: (C) the result of an error by an early scientist.

Chapter 3 1 The three effects of an electric current are the (A) chemical, heating, and lighting effects.

(B) heating, lighting, and sound effects.

(C) lighting, magnetic, and sound effects.

(D) magnetic, chemical, and heating effects.

Answer: (D) magnetic, chemical, and heating effects.

2 The SI definition of an ampere is based on the current's (A) chemical effect.

(B) heating effect.

(C) magnetic effect.

(D) lighting effect.

Answer: (C) magnetic effect.

3 The SI symbol for the ampere is: (A) amp (B) A (C) a (D) I Answer: (B) A 4 A coulomb is used to measure the (A) rate of flow of current.

(B) rate of flow of charge.

(C) quantity of charge.

(D) quantity of electrons.

Answer: (C) quantity of charge.

5 A coulomb is equivalent to (A) an ampere per second.

(B) an ampere second.

(C) 6.24 x 10-18 electrons.

(D) the charge on 6.24 x 10-18 electrons.

Answer: (B) an ampere second.

6 The amount of charge transported by a current of 12 mA during a period of 3 s is: (A) 36 mC (B) 250 mC

(C) 4 C (D) 36 C Answer: (A) 36 mC 7 15 mC of charge is transported past a point in a circuit for 5 min. The current flowing during that period is (A) 50 microamperes (B) 3 milliamperes (C) 50 milliamperes (D) 3 amperes Answer: (A) 50 microamperes

Chapter 4 1

Electrons are made to drift through a metal conductor due to (A) their attraction to an external positive charge and repulsion by an external negative charge (B) their attraction to an external negative charge and repulsion by an external positive charge (C) the chemical effect of the current (D) the difference in pressure between opposite ends of the conductor

Answer: (A) their attraction to an external positive charge and repulsion by an external negative charge 2

The area surrounding a stationary electric charge, in which the effects of that charge may be observed is called (A) a gravitational field (B) a magnetic field (C) an electric field (D) a force field

Answer: (C) an electric field 3

Moving a negative charge in the direction of the field, described above, will (A) increase the potential of that charge (B) decrease the potential of that charge (C) have no effect on the potential of that charge (D) reverse the polarity of that charge

Answer: (A) increase the potential of that charge 4

A potential difference exists between charges located at (A) different points within a magnetic field (B) different points within an electric field (C) opposite ends of a conductor (D) different heights above the ground

Answer: (B) different points within an electric field 5

An object that has acquired a 'positive' potential (A) has less electrons than protons (B) is less negative than another object (C) can be either a or b (D) is neither a nor b

Answer: (C) can be either a or b 6

The unit for potential difference, the volt, is defined in terms of (A) the work done in moving a charge between two points

(B) the difference in charge between two points (C) the difference in energy between two points (D) the difference in energy between a point and that of earth Answer: (A) the work done in moving a charge between two points 7

Voltage' is another term for (A) potential (B) potential difference (C) electromotive force (D) energy-difference

Answer: (B) potential difference 8

The earth is generally considered to have a _______ of zero volts (A) potential (B) potential difference (C) electromotive force (D) energy level

Answer: (A) potential 9

The nominal __________ between the line and neutral of a 13-A socket outlet is 230 V (A) voltage (B) voltage difference (C) voltage drop (D) potential

Answer: (A) voltage 10 A line conductor has a nominal __________ of 230 V with respect to the neutral conductor (A) voltage (B) voltage difference (C) electromotive force (D) potential Answer: (D) potential 11 A battery aquires a potential difference across its terminals due to (A) its stored charge (B) charge separation (C) the type of electrolyte used (D) electrolysis Answer: (B) charge separation

Chapter 5 1

Resistance acts to (A) slow down the current drifting in a conductor (B) decrease the current drifting in a conductor (C) increase the current drifting ina conductor (D) limit the current drifting in a conductor

Answer: (D) limit the current drifting in a conductor 2

The resistance of a conductor will increase if the (A) length of the conductor is reduced (B) cross-sectional area of the conductor is reduced (C) resistivity of the conductor is reduced (D) the current through the conductor is reduced

Answer: (B) cross-sectional area of the conductor is reduced 3

Doubling the diameter of a circular conductor will act to (A) double its resistance (B) half its resistance (C) reduce its resistance by a quarter (D) quadruple its resistance

Answer: (C) reduce its resistance by a quarter 4

A material's resistivity varies with (A) its length (B) its cross-sectional area (C) its temperature (D) the shape of its cross-section

Answer: (C) its temperature 5

The SI unit for resistivity is the (A) ohm (B) ohm per metre (C) ohm metre (D) ohm per cubic metre

Answer: (C) ohm metre 6

Halving the current through a conductor will (A) halve its resistance (B) double its resistance (C) quadruple its resistance

(D) have no effect on its resistance Answer: (D) have no effect on its resistance 7

Increasing the temperature of a pure metal conductor will generally (A) reduce its resistance (B) increase its resistance (C) have no effect on its resistance (D) either a or b

Answer: (B) increase its resistance 8

Increasing the temperature of most insulating materials will (A) reduce their resistance (B) increase their resistance (C) have no effect on their resistance (D) either a or b

Answer: (A) reduce their resistance 9

The 'ohm' is defined in terms of the (A) ratio of voltage to current (B) resisitivity of a material (C) length, cross-sectional area, and resistivity of a conductor (D) the type of conductor

Answer: (A) ratio of voltage to current 10 The insulation resistance for a length of cable is 100 megohms. What would be its value if the cable were five times as long?

(A) 20 megohms (B) 50 megohms (C) 100 megohms (D) 500 megohms Answer: (A) 20 megohms 11 The 'a.c. resistance' is of a conductor is __________ than its d.c. resistance, due to a property called __________ (A) slightly lower, reactance (B) slightly lower, 'skin effect' (C) slightly higher, reactance (D) slightly higher, 'skin effect' Answer: (D) slightly higher, 'skin effect' 12 A.C. resisitance' is caused by a conductor's

(A) increase in resistivity due to frequency (B) loss of effective c.s.a. due to frequency (C) increase in collisions between electrons due to frequency (D) increase in temperature due to frequency Answer: (B) loss of effective c.s.a. due to frequency

Chapter 6 1

In the electrical industry, 'wires' are generally referred to as (A) flex' (B) conductors' (C) cores' (D) cables'

Answer: (B) conductors' 2

Place the following conductors in order, from best to worst in terms of their conductivity: aluminium, silver, gold, and copper (A) gold, silver, copper, aluminium (B) silver, gold, copper, aluminium (C) silver, copper, gold, aluminium (D) silver, copper, aluminium, gold

Answer: (C) silver, copper, gold, aluminium 3

What property makes aluminium generally unsuitable for domestic wiring systems?

(A) poor conductivity compared to copper (B) unreliable pressure connections due to 'cold flow' (C) poor conducting quality of its corrosive film (D) low melting point

Answer: (B) unreliable pressure connections due to 'cold flow' 4

A 'cable' consists of (A) one or more conductors (B) one or more insulated conductors (C) one or more insulated conductors enclosed in a protective sheath

Answer: (C) one or more insulated conductors enclosed in a protective sheath 5

The term, 'live conductors', refers to a cable's (A) line conductor(s) (B) neutral conductor (C) line and neutral conductors (D) line, neutral, and earth conductors

Answer: (C) line and neutral conductors 6

A cable, comprising a line, neutral, and protective (earth) conductor, is termed a (A) single-core conductor' (B) two-core conductor' (C) three-core conductor'

Answer: (B) two-core conductor' 7

Stranded conductors are manufactured to (A) ease their manufacture (B) increase their current ratings (C) increase the flexibility of a cable (D) improve their heat dissipation

Answer: (C) increase the flexibility of a cable 8

For a stranded '7/0.85' cable, the figure '0.85' refers to the (A) the diameter of individual strands (B) the cross-sectional area of individual strands (C) the diameter of the conductor (D) the cross-sectional area of the conductor

Answer: (A) the diameter of individual strands 9

Cables with 'wedge-shaped' cores are manufactured to (A) improve their current-carrying capacity (B) reduce the electrical stress within their insulation (C) improve their flexibility (D) reduce their overall diameter

Answer: (D) reduce their overall diameter 10 The purpose of a cable's outer sheath is to (A) provide limited mechanical protection (B) prevent the ingress of moisture (C) contain the individual cores (D) all of the above Answer: (D) all of the above 11 The purpose of armouring a cable is to (A) protect it against mechanical damage (B) relieve and electric stress (C) prevent the ingress of moisture (D) all of the above Answer: (A) protect it against mechanical damage 12 Insulation is specified, within the UK's Wiring Regulations, in terms of (A) the materials from which it is manufactured (B) its anticipated operating temperature

(C) its method of manufacture (D) its insulation resistance Answer: (B) its anticipated operating temperature 13 The maximum electric field that can be sustained by a dielectric before breakdown occurs' describes an insulator's (A) insulation resistance (B) dielectric strength (C) resistivity (D) voltage gradient Answer: (B) dielectric strength 14 For cables manufactured for use in the EU, the insulation colour for a line conductor is (A) red (B) brown (C) black (D) blue Answer: (B) brown 15 For cables manufactured for use in the EU, the insulation colour for a neutral conductor is (A) red (B) brown (C) black (D) blue Answer: (D) blue

Chapter 7 1 In increase in resistance as a result of an increase in temperature is typical for most (A) pure-metal conductors (B) insulators (C) semiconductors Answer: (A) pure-metal conductors 2 The resistance of carbon __________ when its temperature increases (A) remains constant (B) increases (C) falls Answer: (C) falls 3 Metal alloys, such as constantan, are designed so that their resistance __________ for variations in temperature (A) remains approximately constant (B) increases significantly (C) falls significantly Answer: (A) remains approximately constant 4 The property of a material which affects its change of resistance for variations in temperature is called its (A) resistivity (B) temperature coefficient of resistivity (C) temperature coefficient of resistance Answer: (C) temperature coefficient of resistance 5 A material whose resistance falls as its temperature increases is said to have a (A) positive temperature coefficient of resistance (B) positive temperature coefficient of resistivity (C) negative temperature coefficient of resistance (D) negative temperature coefficient of resistivity Answer: (C) negative temperature coefficient of resistance 6 The relationship between temperature and resistance, for metal conductors, is linear down to absolute zero (A) TRUE (B) FALSE Answer: (B) FALSE

Chapter 8 1

Which of the following statement most accurately describes Ohm's Law? (A) The current flowing through a conductor is proportional to the voltage across that conductor (B) The current flowing through a conductor is equal to the voltage across that conductor, divided by its resistance (C) The ratio of voltage to current is constant for variations in voltage

Answer: (C) The ratio of voltage to current is constant for variations in voltage 2

Not all materials or devices obey Ohm's Law. Those that do, are termed (A) linear or ohmic (B) non-linear or non-ohmic (C) insulators (D) electrolytes

Answer: (A) linear or ohmic 3

For those materials or devices that obey Ohm's Law, a graph of their voltage against current results in a (A) straight-line graph (B) non-linear graph

Answer: (A) straight-line graph 4

The ratio of voltage to current represents the __________ of a material or device, regardless of whether or not it obeys Ohm's Law (A) conductance (B) resistance (C) resistivity

Answer: (B) resistance 5

When a voltage of 12 V is applied across a resistance of 10 ohms, a current of 1.2 A results.

Does this resistance obey Ohm's Law? (A) yes (B) no (C) there is not enough information to tell

Answer: (C) there is not enough information to tell 6

When a voltage of 200 V is applied across a circuit, the resulting current is 5 A. When the voltage is increased to 300 V, the resulting current is 7.5A. Does the circuit probably obey Ohm's Law? (A) Yes, because the ratio of voltage to current remains constant for a change in voltage (B) No, because a change in voltage results in a different value of current

Answer: (A) Yes, because the ratio of voltage to current remains constant for a change in voltage 7

Does a tungsten lamp filament obey Ohm's Law?

(A) Yes, because it is a pure metal conductor (B) No, because its resistance increases significantly as the voltage applied across it increases Answer: (B) No, because its resistance increases significantly as the voltage applied across it increases 8

When a voltage of 15 V is applied to a resistance of 3 ohms, the resulting current is (A) 0.333 A (B) 5 A (C) 45 A

Answer: (B) 5 A 9

When a voltage of 200 V results in a current of 2.5 A, the resistance of circuit is (A) 500 ohms (B) 80 ohms (C) 12.5 milliohms

Answer: (B) 80 ohms 10 When a current of 3 A passes through a resistance of 75 ohms, the voltage across that resistance must be (A) 0.04 V (B) 25 ohms (C) 225 ohms Answer: (C) 225 ohms

Chapter 9 1 Two identical lamps are connected in series, and draw a current of 5 A from the supply. The current through each lamp is (A) 5 A (B) 2.5 A (C) 2.00A Answer: (A) 5 A 2 The current passing through a circuit comprising components connected in series (A) is the same everywhere in the circuit (B) is largest through the lamp closest to the supply (C) splits at each lamp (D) gets less the further it goes around the circuit Answer: (A) is the same everywhere in the circuit 3 Which of the following statements is correct for a series circuit?

(A) the voltage across each component is the same as the supply voltage (B) the sum of the voltages across each component equals the supply voltage (C) the voltage is the same wherever it is measured (D) the largest voltage appears across the component nearest the supply Answer: (B) the sum of the voltages across each component equals the supply voltage 4 The current supplying a circuit comprising lamps in parallel (A) is the same in each branch (B) is the sum of the currents in each branch (C) passes through each branch Answer: (B) is the sum of the currents in each branch 5 A parallel circuit consists of a number of __________ connected across the same supply (A) individual circuits (B) lamps (C) branches (D) junctions Answer: (C) branches 6 Kirchhoff's Voltage Law applies (A) only to series circuits (B) only to parallel circuits (C) only to series-parallel circuits (D) all circuits

Answer: (D) all circuits 7 Kirchhoff's Current Law applies (A) only to series circuits (B) only to parallel circuits (C) only to series-parallel circuits (D) all circuits Answer: (D) all circuits

Chapter 10 1

An electrochemical cell (A) stores charge (B) produces the electrical charges which then pass through a circuit (C) uses a chemical reaction to separate charges

Answer: (C) uses a chemical reaction to separate charges 2

A disposable cell is classified as (A) a battery (B) a primary cell (C) a secondary cell (D) an electrolytic cell

Answer: (B) a primary cell 3

A rechargeable cell is classified as (A) a battery (B) a primary cell (C) a secondary cell (D) an electrolytic cell

Answer: (C) a secondary cell 4

The capacity of a cell is generally expressed in (A) amperes (B) volts (C) ampere hours (D) watts

Answer: (C) ampere hours 5

The capacity of cells may also be expressed in (A) watt hours (B) hours (C) newton metres (D) kilograms per cubic metre

Answer: (A) watt hours 6

A cell's __________ determines the maximum value of continuous current a cell can supply without overheating (A) capacity (B) discharge rate (C) state of charge (D) relative density

Answer: (B) discharge rate 7

A 'Simple' or 'Voltaic' cell, comprises electrodes of __________ and __________ , with an electrolyte of __________ (A) carbon, zinc, dilute sulfuric acid (B) lead sulfate, lead peroxide, dilute sulfuric acid (C) zinc, copper, dilute sulfuric acid (D) zinc, copper, potassium hydroxide

Answer: (C) zinc, copper, dilute sulfuric acid 8

The electromotive force developed by any chemical cell depends on how far apart the electrodes are (A) in terms of their distance (B) in terms of their resistivities (C) on the electrochemical series

Answer: (C) on the electrochemical series 9

In a cell having electrodes of zinc and copper, the negative electrode is always the (A) zinc electrode (B) copper electrode

Answer: (A) zinc electrode 10 The term 'polarisation' describes (A) the polarity of a cell's electrodes (B) the reverseal of a cell's polarity (C) the formation of hydrogen gas bubbles on the positive electrode Answer: (C) the formation of hydrogen gas bubbles on the positive electrode 11 The effect of 'polarisation' is to (A) determine the direction of current supplied by the cell (B) reverse the direction of current supplied by the cell (C) significantly reduce the electromotive force produced by the cell Answer: (C) significantly reduce the electromotive force produced by the cell 12 The electrolyte used in a 'dry Leclanche' cell is a (A) dilute sulfuric acid (B) manganese dioxide gel (C) manganese dioxide and powdered carbon (D) ammonium chloride gel Answer: (D) ammonium chloride gel

13 The purpose of manganese dioxide and powdered carbon mixture in a 'dry Leclanche' cell is to (A) act as an electrolyte (B) reduce the cell's internal resistance (C) act as a depolarising agent (D) turn the electrolyte into a paste Answer: (C) act as a depolarising agent 14 Silver-oxide cells and mercury cells offer the following advantage/advantages: (A) high capacity in comparison with their size (B) long shelf life (C) are small enough to be used in watches, hearing aids, etc.

(D) each of the above Answer: (D) each of the above 15 A fully-charged lead-acid cell comprises electrodes of __________ and __________, and an electrolyte of __________.

(A) lead dioxide, metallic lead, dilute sulfuric acid (B) lead sulfate, lead peroxide, dilute sulfuric acid (C) lead sulfate, metallic lead, dilute sulfuric acid (D) lead dioxide, metallic lead , concentrated sulfuric acid Answer: (A) lead dioxide, metallic lead, dilute sulfuric acid 16 The state of charge of a lead-acid cell may be determined by measuring its (A) voltage (B) current (C) relative density (D) temperature Answer: (C) relative density 17 When a lead-acid cell de-energizes, both electrodes undergo a chemical reaction, with each changing to (A) metallic lead (B) lead dioxide (C) lead peroxide (D) lead sulfate Answer: (D) lead sulfate 18 As a lead-acid cell de-energizes, its relative density (A) remains approximately constant (B) increases towards 1.27

(C) falls towards 1.17 (D) increases towards 1.84.

Answer: (C) falls towards 1.17 19 The device used to measure a lead-acid cell's relative density is called a (A) hydrometer (B) hygrometer (C) densiometer (D) calorimeter Answer: (A) hydrometer 20 Memory effect' and 'voltage depression' are two drawbacks associated with (A) lead-acid cells (B) nickel-cadmium cells (C) lithium-ion cells (D) alkaline cells Answer: (B) nickel-cadmium cells 21 The major advantages associated with lithium-ion cells are (A) high capacity/weight ratio (B) no 'memory effect' or 'voltage depression' problems (C) capable of large number of energizing/de-energizing cycles (D) all of the above Answer: (D) all of the above 22 The legislation which deals with the responsible disposal of used cells and batteries is the (A) Electricity Supply Regulations (B) Health and Safety at Work Regulations (C) Waste Electronic and Electrical Equipment Directive (D) Electricity at Work Act Answer: (C) Waste Electronic and Electrical Equipment Directive 23 When three identical cells are connected in series, the resulting e.m.f. is __________ that of one cell (A) one-third (B) the same as (C) three times Answer: (C) three times 24 When three identical cells are connected in series, the resulting current capacity is __________ that of one cell

(A) one-third (B) the same as (C) three times Answer: (B) the same as 25 When three identical cells are connected in parallel, the resulting e.m.f. is __________ times that of one cell (A) one-third (B) the same as (C) three times Answer: (B) the same as 26 When three identical cells are connected in parallel, the resulting current capacity is __________ times that of one cell (A) one-third (B) the same as (C) three times Answer: (C) three times 27 When connecting cells in series or parallel to create a battery, (A) they should all be of the same type (B) they should all be of the same brand (C) their capacities may vary (D) they must all be disposable types Answer: (A) they should all be of the same type

Chapter 11 1 A voltage source's internal resistance is effectively in __________ with its external load (A) series (B) parallel (C) series-parallel Answer: (A) series 2 The potential difference appearing across a voltage source's terminals, when there is no load connected is termed its (A) no-load voltage (B) open-circuit voltage (C) electromotive force (D) any of the above Answer: (D) any of the above 3 The potential difference appearing across a voltage source's terminals, when supplying a load, will be (A) lower than its e.m.f.

(B) equal to its e.m.f.

(C) greater than its e.m.f Answer: (A) lower than its e.m.f.

4 As the load increases, the terminal voltage of a voltage source will (A) decrease further (B) remain unaffected (C) increase further Answer: (A) decrease further 5 The sum of the voltage drops around any closed loop, including the internal voltage drop within a voltage source, is equal to the (A) internal voltage drop (B) e.m.f. of the voltage source (C) external voltage drop Answer: (B) e.m.f. of the voltage source 6 A battery has an e.m.f. of 12 V and an internal resistance of 500 milliohms. What will be its terminal voltage, when supplying a load of 20 ohms?

(A) 0.293 V (B) 11.7 V (C) 12V Answer: (B) 11.7 V

7 If the load supplied by the battery, described above, should increase, what will happen to its terminal voltage?

(A) It will decrease further (B) It will remain unchanged (C) It will increase Answer: (A) It will decrease further 8 What's likely to happen to the internal resistance of a generator when its load increases?

(A) It will remain the same (B) It will increase, due to an increase in its temperature (C) It will decrease, due to a decrease in its temperature Answer: (B) It will increase, due to an increase in its temperature

Chapter 12 1

The process by which one form of energy is converted into another form is called (A) torque (B) work (C) heat (D) power

Answer: (B) work 2

The process by which energy is transferred from a warmer body to a cooler body is called (A) temperature (B) work (C) heat (D) power

Answer: (C) heat 3

The rate at which one form of energy is converted into another form is called (A) velocity (B) work (C) heat (D) power

Answer: (D) power 4

The rate at which energy is transferred from a warmer body to a cooler body is called (A) force (B) work (C) heat (D) power

Answer: (D) power 5

The SI unit for energy is the (A) Celsius (B) kelvin (C) joule (D) watt

Answer: (C) joule 6

The SI unit for work is the (A) metre per second (B) newton metre (C) joule

(D) watt Answer: (C) joule 7

The SI unit for heat transfer is the (A) Celsius (B) kelvin (C) joule (D) watt

Answer: (C) joule 8

The SI unit for power is the (A) unit (B) watt hour (C) joule (D) watt

Answer: (D) watt 9

The SI unit for the rate of heat transfer is the (A) Celsius per second (B) kelvin per second (C) joule per second (D) watt

Answer: (D) watt 10 The SI unit for the rate of doing work is the (A) newton metre (B) watt hour (C) joule (D) watt Answer: (D) watt 11 As a customer of your electricity supply company, your energy consumption is measured in (A) kilowatts per hour (B) kilowatt hours (C) megajoules (D) kilowatts Answer: (B) kilowatt hours 12 How much power is supplied to a 100 W lamp over a period of 3 hours?

(A) 33.3 W (B) 100 W (C) 300 W (D) 300 W.h Answer: (B) 100 W 13 What will happen to the power of a fixed resistance if the applied voltage is doubled?

(A) it will reduce by half (B) it will also double (C) it will reduce by one-quarter (D) it will quadruple Answer: (D) it will quadruple 14 What will happen to the power of a fixed resistance if the current through it is halved?

(A) it will reduce by half (B) it will also double (C) it will reduce by one-quarter (D) it will quadruple Answer: (C) it will reduce by one-quarter 15 If doubling the voltage causes the resulting current to double, what will happens to the power of the circuit?

(A) it will reduce by half (B) it will also double (C) it will reduce by one-quarter (D) it will quadruple Answer: (D) it will quadruple 16 How much energy is supplied to a 2000-W circuit over a period of 10 min?

(A) 1.2 MJ (B) 20 kJ (C) 1.2 W/min (D) 20 kW/s Answer: (A) 1.2 MJ 17 The term 'power loss', when applied to a transmission cable, actually refers to (A) the amount of power lost through heat transfer (B) the rate at which power is lost through heat transfer (C) the amount of energy lost through heat transfer (D) the rate at which energy is lost through heat transfer

Answer: (D) the rate at which energy is lost through heat transfer 18 The 'power rating' of an electric motor refers to its (A) input power (B) output power (C) the difference between its output and input power (D) its energy consumption Answer: (B) output power 19 The 'efficiency' of a motor, or any other electrical machine, is equal to (A) its input power minus its output power (B) its output power minus its input power (C) its input power divided by its output power (D) its output power divided by its input power Answer: (D) its output power divided by its input power 20 The 'losses' of a motor, or any other electrical machine, is equal to (A) its input power minus its output power (B) its output power minus its input power (C) its input power divided by its output power (D) its output power divided by its input power Answer: (A) its input power minus its output power 21 What is meant by the term 'windage loss', when applied to a rotating machine?

(A) energy-loss in the machine's windings (B) failure to produce torque due to a damaged winding (C) energy-loss overcoming air resistance Answer: (C) energy-loss overcoming air resistance 22 A higher-wattage lamp has a __________ resistance than a lower-wattage lamp (A) higher (B) lower Answer: (B) lower 23 A 100-W/230-V lamp is connected in series with a 60-W/230-V lamp, across a 230-V supply. Which lamp will be the brightest?

(A) 100-W lamp (B) 60-W lamp Answer: (B) 60-W lamp

24 The sum-total of all the energies associated with the molecules that make up a body is called its (A) heat energy (B) thermal energy (C) internal energy (D) work Answer: (C) internal energy 25 The difference between the work done on an electric kettle and the heat lost to the surroundings is equal to the (A) increase in temperature of the kettle (B) increase in the power of the kettle (C) increase in the internal energy of the kettle (D) efficiency of the kettle Answer: (C) increase in the internal energy of the kettle 26 Which has the higher internal energy? A given mass of water at 100 degrees Celsius or the same mass of steam at 100 degrees Celsius?

(A) water (B) steam (C) neither -they will both have the same amount of internal energy Answer: (B) steam

Chapter 13 1

When freely suspended, a magnet will come to rest aligned with the magnetic field linking (A) True North and True South (B) Magnetic North and Magnetic South

Answer: (B) Magnetic North and Magnetic South 2

The term, 'Magnetic North', describes (A) a location near True North (B) the magnetic polarity of a location near Magnetic North

Answer: (A) a location near True North 3

The magnetic poles of a magnet are named after (A) the directions in which they point (B) the magnetic polarities that attract them

Answer: (A) the directions in which they point 4

The magnetic polarity of Magnetic North is a (A) north pole (B) south pole

Answer: (B) south pole 5

The end of a compass needle which points to Magnetic North is a (A) north magnetic pole (B) a south magnetic pole

Answer: (A) north magnetic pole 6

The fundamental law of magnetism states that 'like poles __________' (A) attract each other (B) repel each other

Answer: (B) repel each other 7

The area surrounding a magnet in which its effects may be observed is termed (A) a magnetic field (B) magnetic flux

Answer: (A) a magnetic field 8

Lines of magnetic flux (A) are invisible, but can be detected with sensitive instruments (B) do not exist, but provide a model to help us visualise a magnetic field (C) were discovered by the ancient Chinese

(D) were discovered by the ancient Greeks Answer: (B) do not exist, but provide a model to help us visualise a magnetic field 9

The 'direction' of magnetic flux lines is defined in terms of the direction in which __________ when placed within the magnetic field (A) an isolated positive charge will move (B) an isolated negative charge will move (C) a compass needle will point

Answer: (C) a compass needle will point 10 The 'direction' of magnetic flux lines is defined as (A) north to south (B) south to north Answer: (A) north to south 11 The poles of an unmarked magnet can be identified using a compass, which will always point to the magnet's (A) north pole (B) south pole Answer: (B) south pole 12 Sprinkling iron filings over a sheet of card resting on a magnet will reveal (A) the polarity of the magnet's poles (B) the direction of the magnet's flux lines (C) the pattern formed by the magnet's magnetic field Answer: (C) the pattern formed by the magnet's magnetic field 13 The intensity of a magnetic field is termed its __________, whose SI unit is the __________ (A) flux density, tesla (B) flux density, weber (C) magnetic field strength, tesla (D) magnetic field strength, weber Answer: (A) flux density, tesla 14 The intensity of the external magnetic field surrounding a magnet is greatest (A) at the magnet's poles (B) midway between the magnet's poles Answer: (A) at the magnet's poles

15 Soft' magnetic materials are _________ to magnetise, and __________ their magnetism once the external magnetising force is removed (A) easy, lose (B) easy, retain (C) hard, lose (D) hard, retain Answer: (A) easy, lose 16 Hard' magnetic materials are __________ to magnetise, and __________ their magnetism once the external magnetising force is removed (A) easy, lose (B) easy, retain (C) hard, lose (D) hard, retain Answer: (D) hard, retain 17 Soft' magnetic materials are used to make __________ magnets (A) permanent (B) temporary Answer: (B) temporary 18 Hard' magnetic materials are used to make __________ magnets (A) permanent (B) temporary Answer: (A) permanent 19 Steel is generally considered to be a '__________' magnetic material, and can be used to make __________ magnets (A) hard, temporary (B) hard, permanent (C) soft, temporary (D) soft, permanent Answer: (B) hard, permanent 20 Soft iron is generally considered to be a '__________' magnetic material, and can be used to make __________ magnets (A) hard, temporary (B) hard, permanent (C) soft, temporary (D) soft, permanent

Answer: (C) soft, temporary 21 A 'domain' is the name given to (A) an atom or molecule that behaves like a tiny magnet (B) an electron that behaves like a tiny magnet (C) any tiny magnet (D) the area near the pole of a magnet Answer: (A) an atom or molecule that behaves like a tiny magnet 22 When a magnet's 'domains' are all aligned, the magnet is said to be (A) hard' (B) permanent' (C) saturated' Answer: (C) saturated' 23 When a magnet is broken in two, the result is (A) two, separate, magnets (B) two magnets, each having just one pole (C) two magnets with like poles (D) the loss of the magnetic field Answer: (A) two, separate, magnets

Chapter 14 1

A conductor that carries an electric current is surrounded by a (A) perpendicular electric field (B) concentric electric field (C) perpendicular magnetic field (D) concentric magnetic field

Answer: (D) concentric magnetic field 2

A dot shown within a circle representing an end-on view of a conductor is the convention used to indicate that current is (A) flowing towards you (B) flowing away from you

Answer: (A) flowing towards you 3

The 'direction' of lines of magnetic flux are determined by the direction a __________ would point when placed within the field (A) permanent magnet (B) compass needle (C) gaussmeter

Answer: (B) compass needle 4

The SI unit of measurement for magnetic flux is the (A) weber (B) tesla (C) gauss (D) maxwell

Answer: (A) weber 5

For conventional flow, the direction of the magnetic field surrounding a straight conductor can be determined using the (A) corkscrew' rule (B) right-hand 'grip' rule (C) either of the above

Answer: (C) either of the above 6

What is the magnetic polarity of the visible face of a loop of wire, around which conventional flow is counter-clockwise?

(A) north (B) south

Answer: (A) north

7

The magnetic polarity of a coil, around which conventional current direction is known, may be determined using (A) Fleming's Right-Hand Rule (B) Fleming's Left-Hand Rule (C) the right-hand 'grip' rule (D) the left-hand 'grip' rule

Answer: (C) the right-hand 'grip' rule 8

If each of two parallel conductors carry currents flowing in the same direction, then the two conductors (A) will repel each other (B) will attract each other (C) will have no effect upon each other

Answer: (B) will attract each other 9

Flux density is defined as the (A) flux per unit area, measured in webers (B) flux per unit area, measured in teslas

Answer: (B) flux per unit area, measured in teslas 10 The SI unit of measurement for magnetic flux density is the (A) weber (B) tesla (C) gauss (D) maxwell Answer: (B) tesla 11 Magnetic flux density is at its greatest __________ the poles of an electromagnet (A) closest to (B) furthest away from Answer: (A) closest to 12 Which has the greatest effect on increasing the flux density within a current-carrying coil?

(A) doubling the number of turns (B) halving the cross-sectional area (C) reducing its length by half (D) inserting an iron core Answer: (D) inserting an iron core 13 When using Fleming's Left-Hand Rule, the first finger represents __________, the second finger represents __________, and the thumb represents __________

(A) force, field, current (B) field, current, force (C) current, force, field Answer: (B) field, current, force 14 A current-carrying conductor, placed within a permanent magetic field, will be forced out of that field. This is an example of (A) motor action (B) generator action (C) electromagnetic induction Answer: (A) motor action 15 Motors, moving-coil measuring instruments, and dynamic loudspeakers all work on the principle of (A) motor action (B) generator action (C) electromagnetic induction Answer: (A) motor action 16 The components of a d.c. motor which ensure that the rotor continues to rotate in the same direction are the (A) slip rings and brushes (B) split-ring commutator and brushes (C) diodes Answer: (B) split-ring commutator and brushes

Chapter 15 1

A closed path within an electrical machine in which lines of magnetic flux are confined is generically termed a (A) stator' (B) rotor' (C) core' (D) magnetic circuit'

Answer: (D) magnetic circuit' 2

A magnetic circuit's magnetomotive force is equivalent to the __________ in an electric circuit (A) voltage gradient (B) voltage (C) resistance (D) current

Answer: (B) voltage 3

A magnetic circuit's magnetic flux is equivalent to the __________ in an electric circuit (A) voltage gradient (B) voltage (C) resistance (D) current

Answer: (D) current 4

A magnetic circuit's reluctance is equivalent to the __________ in an electric circuit (A) voltage gradient (B) voltage (C) resistance (D) current

Answer: (C) resistance 5

A magnetic circuit's magnetic field strength is equivalent to the __________ in an electric circuit (A) voltage gradient (B) voltage (C) resistance (D) current

Answer: (A) voltage gradient 6

The SI unit of measurement for magnetomotive force is the (A) weber (B) ampere per weber

(C) ampere (D) ampere per metre Answer: (C) ampere 7

The SI unit of measurement for magnetic flux is the (A) weber (B) ampere per weber (C) ampere (D) ampere per metre

Answer: (A) weber 8

The SI unit of measurement for reluctance is the (A) weber (B) ampere per weber (C) ampere (D) ampere per metre

Answer: (B) ampere per weber 9

The SI unit of measurement for magnetic field strength is the (A) weber (B) ampere per weber (C) ampere (D) ampere per metre

Answer: (D) ampere per metre 10 The relationship between magnetomotive force, magnetic flux, and reluctance is (A) mmf = flux x reluctance (B) mmf = flux/reluctance (C) mmf = reluctance/flux Answer: (A) mmf = flux x reluctance 11 In a magnetic circuit, the equivalent of 'conductivity' is called (A) resistivity' (B) permittivity' (C) permeability' (D) susceptibility' Answer: (C) permeability' 12 Diamagnetic' materials cause a slight __________ in the flux density within that material, when placed within a uniform magnetic field

(A) increase (B) decrease Answer: (B) decrease 13 paramagnetic' materials cause a slight __________ in the flux density within that material, when placed within a uniform magnetic field (A) increase (B) decrease Answer: (A) increase 14 An 'homogenous' magnetic circuit is one in which the magnetic flux is formed within (A) entirely the same material (B) different materials (C) ferromagnetic materials (D) non-ferromagnetic materials Answer: (A) entirely the same material 15 An 'compound' magnetic circuit is one in which the magnetic flux is formed within (A) entirely the same material (B) different materials (C) ferromagnetic materials (D) non-ferromagnetic materials Answer: (B) different materials 16 A motor's magnetic circuit is an example of (A) an homogenous circuit (B) a compound circuit Answer: (B) a compound circuit 17 A transformer's core is an example of (A) an homogenous magnetic circuit (B) a compound magnetic circuit Answer: (A) an homogenous magnetic circuit 18 A graph which plots the relationship between magnetic field strength and magnetic flux density is called a (A) magnetisation curve' (B) B-H curve' (C) either of the above

Answer: (C) either of the above 19 The upper end of the above curve starts to flatten off, as the sample of magnetic material approaches (A) remenance (B) saturation (C) coercivity (D) hysteresis Answer: (B) saturation 20 When the magnetic field strength is reduced towards zero, the resulting change in flux density tends to lag behind, due to a property called (A) remenance (B) saturation (C) coercivity (D) hysteresis Answer: (D) hysteresis 21 When the magnetic field strength reaches zero, the sample of magnetic material retains some flux density, called (A) remenance (B) saturation (C) coercivity (D) hysteresis Answer: (A) remenance 22 To completely remove any remaining magnetic flux density from the sample of magnetic material, the magnetic field strength must be reversed to a value termed its (A) remenance (B) saturation (C) coercivity (D) hysteresis Answer: (C) coercivity 23 The curve resulting from plotting the magnetic flux density against the magnetic field strenght applied over a complete cycle, is termed a (A) magnetisation curve (B) B-H curve (C) hysteresis curve Answer: (C) hysteresis curve

24 The volume enclosed by the above curve represents the __________ necessary to completely magnetise and demagnetise a sample of magnetic material in both directions (A) effort (B) energy (C) power Answer: (B) energy 25 A small area enclosed by the above curve is typical of __________ magnetic materials, such as __________ (A) soft, steel (B) soft, iron (C) hard, steel (D) hard, iron Answer: (B) soft, iron 26 A large area enclosed by the above curve is typical of __________ magnetic materials, such as __________ (A) soft, steel (B) soft, iron (C) hard, steel (D) hard, iron Answer: (C) hard, steel

Chapter 16 1

Relative motion between a conductor and a magnetic field will result in a __________ being induced into the conductor (A) voltage (B) current

Answer: (A) voltage 2

The direction of the induced __________ depends on the __________ of motion of the __________ relative to the __________ (A) voltage, velocity, conductor, field (B) voltage, direction, conductor, field (C) current, velocity, conductor, field (D) current, direction, field, conductor

Answer: (B) voltage, direction, conductor, field 3

The above action is generically called (A) motor action' (B) generator action'

Answer: (B) generator action' 4

The potential difference appearing across the ends of a conductor as it passes perpendicularly through a magnetic field depends upon (A) the flux density of the field (B) the length of the conductor within the field (C) the velocity of the conductor (D) all the above

Answer: (D) all the above 5

The potential difference appearing across the ends of a conductor if as it passes through a magnetic field also depends on the __________ of the angle at which the flux lines are 'cut' (A) sine (B) cosine (C) tangent

Answer: (A) sine 6

The direction of the potential difference appearing across the ends of a conductor as it passes through a magnetic field may be determined using (A) Fleming's Left-Hand Rule (conventional flow) (B) Fleming's Right-Hand Rule (conventional flow)

Answer: (B) Fleming's Right-Hand Rule (conventional flow) 7

For the above rule, the first finger represent the __________, the second finger represents the __________, and the thumb indicates the ___________

(A) field, current, motion (B) voltage, motion, field (C) field, voltage, motion (D) field, motion, current Answer: (C) field, voltage, motion 8

The statement that 'any current resulting from the potential difference induced into a conductor moving through a magnetic field must act in a direction such that its own magnetic field will oppose the motion of that conductor', is known as (A) Faraday's Law (B) Maxwell's Law (C) Law of the conservation of energy (D) Lenz's Law

Answer: (D) Lenz's Law 9

If a permanent magnet is moved towards a coil that forms a closed circuit, the polarity of its resulting magnetic field will (A) oppose the movement of the magnet (B) assist the movement of the magnet (C) will have no effect on the movement of the magnet

Answer: (A) oppose the movement of the magnet 10 If a permanent magnet is moved away from a coil that forms a closed circuit, the polarity of its resulting magnetic field will (A) oppose the movement of the magnet (B) assist the movement of the magnet (C) will have no effect on the movement of the magnet Answer: (A) oppose the movement of the magnet 11 Any change in the current flowing through a coil will induce a __________ into that coil, which will __________ the change in that current (A) current, oppose (B) current, reinforce (C) voltage, oppose (D) voltage, reinforce Answer: (C) voltage, oppose 12 The process, described above, is termed (A) self induction (B) mutual induction (C) coefficient of coupling

(D) conservation of energy Answer: (A) self induction 13 Doubling the number of turns in a coil will __________ its inductance (A) quadruple (B) double (C) halve (D) quarter Answer: (A) quadruple 14 Doubling the cross-sectional area of a coil will __________ its inductance (A) quadruple (B) double (C) halve (D) quarter Answer: (B) double 15 Doubling the length of a coil will __________ its inductance (A) quadruple (B) double (C) halve (D) quarter Answer: (C) halve 16 The SI unit of measurement of inductance is the (A) henry (B) weber per metre (C) farad (D) ampere turn Answer: (A) henry 17 The most effective way of significantly increasing the inductance of a coil is to (A) increase the number of turns (B) reduce the length of the coil (C) increase its cross-sectional area (D) insert a ferromagnetic core Answer: (D) insert a ferromagnetic core 18 If a coil is suddenly connected to a d.c. supply, the resulting current would be limited by the __________ of that coil

(A) inductance (B) resistance (C) number of turns (D) permeability Answer: (B) resistance 19 When a coil is suddenly connected to a d.c. supply, if the initial rate of increase in current was maintained, it would reach its maximum value (A) instantaneously (B) in a period of time called a 'time constant' (C) in a period of time equivalent to five 'time constants' Answer: (B) in a period of time called a 'time constant' 20 The actual time taken by the current, in the above question, to reach its maximum value will be (A) instantaneously (B) in a period of time called a 'time constant' (C) in a period of time equivalent to five 'time constants' Answer: (C) in a period of time equivalent to five 'time constants' 21 If a coil of inductance 0.2 H and negligible resistance, carrying a steady d.c. current were suddenly short-circuited, using a resistance of 500 ohm, the current would reach zero in (A) 0.4 ms (B) 2 ms (C) 100 s (D) 500 s Answer: (B) 2 ms 22 If a change in current in one coil induces a potential difference in a second coil through (A) inductance (B) self inductance (C) mutual inductance (D) motor action Answer: (C) mutual inductance 23 Two separate coils, wound around a common core, in which a changing current in one coil induces a potential difference into a second coil, is called (A) an inductor (B) a mutual inductor (C) a transformer (D) an autotransformer

Answer: (C) a transformer 24 The term, 'coupled', when applied to two coils, describes (A) the degree by which magnetic flux is able to link the two coils (B) how physically close they are together (C) when they share a common core Answer: (A) the degree by which magnetic flux is able to link the two coils 25 Any magnetic flux produced in one coil that doesn't link with a second coil sharing the same magnetic circuit is termed (A) redundant flux (B) leakage flux (C) fringing Answer: (B) leakage flux 26 For an 'ideal' transformer, the voltage ratio is equal to (A) turns ratio (B) reciprocal of the turns ratio (C) current ratio Answer: (A) turns ratio 27 A transformer's 'primary' winding is the (A) higher-voltage winding (B) lower-voltage winding (C) winding connected to the supply (D) wingind connected to the load Answer: (C) winding connected to the supply 28 The terms, 'choke', 'reactor', and 'ballast' are (A) alternative names for an inductor (B) alternative names for a coil (C) applications for an inductor Answer: (C) applications for an inductor 29 When determining the total inductance, inductors in series are treated like resistors in __________, and inductors in parallel are treated like resistors in __________ (A) series, parallel (B) parallel, series Answer: (A) series, parallel

Chapter 17 1

A capacitor is a device that will store (A) charge (B) energy (C) current (D) power

Answer: (B) energy 2

Capacitors are named according to their (A) method of construction (B) types of plate (C) application (D) dielectric

Answer: (D) dielectric 3

During 'charging', a capacitor will transfer __________ from one plate to the other (A) charge (B) energy (C) current (D) voltage

Answer: (A) charge 4

A capacitor will stop charging, when the potential difference across its plates reaches the same __________ as the external supply (A) polarity (B) charge (C) potential (D) potential difference

Answer: (D) potential difference 5

A charging capacitor will aquire the __________ polarity __________ the external supply voltage (A) opposite, to (B) same, as

Answer: (B) same, as 6

Energy supplied to a capacitor is stored (A) in its dielectric.

(B) on its positive plate (C) on its negative plate (D) on both its plates

Answer: (A) in its dielectric.

7

By convention, the 'charge' on a capacitor is the amount of __________ charge accumulated on its __________ plate, expressed in coulombs (A) positive, negative (B) negative, positive (C) negative, negative

Answer: (C) negative, negative 8

Doubling the area of overlap of the plates of a capacitor will __________ its capacitance (A) quarter (B) halve (C) double (D) quadruple

Answer: (C) double 9

Halving the distance between the plates of a capacitor will __________ its capacitance (A) quarter (B) halve (C) double (D) quaduple

Answer: (C) double 10 The __________ of the dielectric will have a great impact on the capacitance of a capacitor (A) permittivity (B) permeability (C) dielectric strength Answer: (A) permittivity 11 The capacitance of a capacitor is directly proportional to the (A) ratio of voltage to charge (B) ratio of charge to voltage (C) product of charge and voltage Answer: (B) ratio of charge to voltage 12 The term, 'displacement current' describes the way in which the dielectric's __________ whenever the potential-difference across a capacitor's plates changes (A) leakage current changes (B) atoms' electron orbits polarise Answer: (B) atoms' electron orbits polarise

13 The effect of an increasing displacement current is to __________ the electric field within the dielectric (A) neutralise (B) increase (C) decrease Answer: (C) decrease 14 A __________ in a capacitor's displacement current will act to __________ its capacitance (A) decrease, decrease (B) decrease, increase (C) rise, increase Answer: (B) decrease, increase 15 A dielectric's dielectric strength __________ to its absolute permittivity (A) bears no relationship (B) is proportional (C) is inversely-proportional Answer: (A) bears no relationship 16 The voltage rating of a capacitor is generally expressed as a __________ (A) d.c. voltage (B) root-mean-square a.c. voltage (C) average a.c. voltage (D) peak a.c. voltage Answer: (A) d.c. voltage 17 The time taken for a capacitor to fully charge is five times the __________ of a capacitive circuit (A) ratio of capacitance to resistance (B) ratio of resistance to capacitance (C) product of resistance and capacitance Answer: (C) product of resistance and capacitance 18 A capacitor always acts to oppose any change in (A) current (B) voltage Answer: (B) voltage 19 When calculating total capacitance, capacitors in __________ are treated like resistors in __________

(A) series, parallel (B) series, series (C) parallel, parallel Answer: (A) series, parallel

Chapter 18 1

The primary reason for generating, transmitting, and distributing alternating current is because (A) there are more applications for a.c. than for d.c.

(B) its voltage levels may be changed easily using transformers (C) a.c. has lower losses than d.c.

(D) a.c. is generally safer than d.c.

Answer: (B) its voltage levels may be changed easily using transformers 2

A four-pole alternator must rotate at what speed in order to generate a voltage at 50 Hz? (A) 12.5 rev/min (B) 25 rev/min (C) 750 Rev/min (D) 1500 rev/min

Answer: (D) 1500 rev/min 3

The highest practical speed of a 50-Hz alternator is (A) 1500 rev/min (B) 3000 rev/min (C) 6000 rev/min (D) 12000 rev/min

Answer: (B) 3000 rev/min 4

Alternators driven by water turbines have __________ poles than those driven by steam, because water turbines rotate at a __________ speed.

(A) more, lower (B) more, higher (C) less, lower (D) less, higher

Answer: (A) more, lower 5

Transmission voltages are as high as possible to reduce the resulting (A) load current (B) voltage drop along the transmission line (C) line losses (D) each of the above

Answer: (D) each of the above 6

In the UK, voltages of 400 kV and 275 kV are used in the __________ system (A) transmission (B) primary distribution

(C) secondary distribution (D) tertiary distribution Answer: (A) transmission 7

In the UK, voltages of 132 kV and 33 kV are used in the __________ system (A) transmission (B) primary distribution (C) secondary distribution (D) tertiary distribution

Answer: (B) primary distribution 8

In the UK, voltages of 11 kV are used in the __________ system (A) transmission (B) primary distribution (C) secondary distribution (D) tertiary distribution

Answer: (C) secondary distribution 9

The maximum value of an a.c. waveform, in either the positive or negative sense, is called its (A) instantaneous value (B) peak-to-peak value (C) amplitude (D) r.m.s value

Answer: (C) amplitude 10 The value of voltage or current, at any specified displacement angle, during a complete cycle is called its (A) instantaneous value (B) average value (C) amplitude (D) r.m.s value Answer: (A) instantaneous value 11 A current, having a root-mean-square of 13 A will do the same amount of work as a d.c. current of (A) 9.2 A (B) 13 A (C) 18.4 A Answer: (B) 13 A

12 A nominal supply voltage of 230 V (a.c.) represents the __________ of the supply (A) average voltage (B) root-mean-square voltage (C) peak voltage (D) peak-to-peak voltage Answer: (B) root-mean-square voltage 13 A sinusoidal voltage, having a root-mean-square value of 400 V, has a peak-to-peak value of (A) 0 V (B) 400 V (C) 566 V (D) 1132 V Answer: (D) 1132 V 14 A sinusoidal voltage, having a root-mean-square value of 400 V, has an average value of (A) 0 V (B) 400 V (C) 566 V (D) 1132 V Answer: (A) 0 V 15 The instantaneous current, at a displacement angle of 30 degrees, of a sinusoidal current having an r.ms. value of 5 A, is (A) 2.5 A (B) 3.54 A (C) 4.33 A (D) 6.12 A Answer: (B) 3.54 A 16 Ammeters and voltmeters are calibrated to measure (A) average values (B) root-mean-square values (C) peak values (D) peak-to-peak values Answer: (B) root-mean-square values 17 A right-angled triangle has a hypotenuse of 10 m and an opposite of 6 m. What is the length of its adjacent side?

(A) 4 m (B) 8 m

(C) 11.7 m Answer: (B) 8 m 18 What is the angle between the adjacent and hypotenuse of the above right-angled triangle?

(A) 36.87 degrees (B) 38.66 degrees (C) 53.13 degrees Answer: (A) 36.87 degrees 19 The length of a phasor usually represents the __________ of an a.c. voltage or current (A) amplitude (B) average value (C) root-mean-square value Answer: (C) root-mean-square value 20 The angle of a phasor, measured counterclockwise from the normal, positive, axis represents a voltage's or current's (A) displacement angle (B) phase angle (C) periodic time (D) frequency Answer: (A) displacement angle

Chapter 19 1

The load current is in phase with the supply current for __________ loads (A) purely resistive (B) purely capacitive (C) purely inductive

Answer: (A) purely resistive 2

The load current lags the supply voltage by 90 degrees for __________ loads (A) purely resistive (B) purely capacitive (C) purely inductive

Answer: (C) purely inductive 3

The load current leads the supply voltage by 90 degrees for __________ loads (A) purely resistive (B) purely capacitive (C) purely inductive

Answer: (B) purely capacitive 4

The opposition to current offered by a purely-capacitive or a purely-inductive load is termed (A) resistance (B) reactance (C) impedance

Answer: (C) impedance 5

The inductive reactance of a load is __________ the supply frequency (A) directly-proportional to (B) inversely-proportional to (C) unaffected by

Answer: (A) directly-proportional to 6

The capacitive reactance of a load is __________ the supply frequency (A) directly-proportional to (B) inversely-proportional to (C) unaffected by

Answer: (B) inversely-proportional to 7

The inductive reactance of a load is directly-proportional to (A) the supply voltage (B) the supply voltage

(C) its self inductance Answer: (C) its self inductance 8

The capacitive reactance of a load is directly-proportional to (A) the supply voltage (B) the supply voltage (C) its capacitance

Answer: (C) its capacitance 9

The opposition to the drift of current in an inductive-reactive circuit is termed (A) resistance (B) inductive reactance (C) impedance (D) 0

Answer: (D) 0 10 The potential-difference across a capacitive-resistive circuit, divided by the load current, is termed (A) resistance (B) capacitive reactance (C) impedance (D) 0 Answer: (D) 0 11 The reference phasor in any a.c. circuit is normally drawn along the (A) horizontal positive axis (B) vertical positive axis (C) horizontal negative axis (D) vertical negative axis Answer: (A) horizontal positive axis 12 The reference phasor for a series a.c. circuit is the __________ phasor (A) voltage (B) current (C) resistance (D) reactance Answer: (B) current 13 Phasors are said to 'rotate' (A) at synchronous speed

(B) clockwise (C) counterclockwise Answer: (C) counterclockwise 14 The impedance of a load is the __________ sum of the load's resistance and reactance (A) algebraic (B) geometric (C) phasor Answer: (C) phasor 15 The phase angle of an a.c. circuit is defined as the 'angle by which the (A) supply voltage leads or lags the load current' (B) load current leads or lags the supply voltage' (C) phasor Answer: (B) load current leads or lags the supply voltage' 16 A 'leading' phase angle indicates a __________ load (A) purely resistive (B) resistive-inductive (C) resistive-capacitive Answer: (C) resistive-capacitive 17 The voltage appearing across a series R-L circuit is the __________ of the voltage-drops across the resistive and inductive components (A) algebraic (B) geometric (C) 0 Answer: (C) 0 18 The voltage appearing across a series R-L circuit may be determined by applying __________ to the voltage-drops across the resistive and inductive components.

(A) simple addition (B) basic trigonometry (C) Pythagoras's Theorem Answer: (C) Pythagoras's Theorem 19 If the voltage drop measured across the resistive component of a series R-C circuit is 90 V and the voltage drop measured across the capacitive component is 120 V, the supply voltage must be (A) 30 V. (B) 150 V.

(C) 210 V (D) 0 Answer: (D) 0 20 To convert a voltage phasor diagram into an impedance diagram, we must __________ voltage phasors __________ the reference phasor.

(A) multiply, by (B) divide, by (C) add the, to (D) subtract the, to Answer: (B) divide, by 21 The impedance of an a.c. series R-L-C circuit is the __________ of the __________, __________, and the __________ (A) vector-sum, resistance, inductive reactance, capacitive reactance (B) algebraic-sum, resistance, inductive reactance, capacitive reactance (C) vector-sum, resistance, inductance, capacitance.

(D) algebraic-sum, resistance, inductance, capacitance Answer: (A) vector-sum, resistance, inductive reactance, capacitive reactance 22 A series a.c. circuit has an inductive reactance of 60 ohms and a capacitive reactance of 20 ohms. The equivalent circuit has a reactance of __________ ohms, and a __________ phase angle (A) 80 ohms, leading (B) 80 ohms, lagging (C) 40 ohms, leading (D) 40 ohms, lagging Answer: (D) 40 ohms, lagging 23 Series resonance can only occur in a __________ a.c. circuit.

(A) purely resistive (B) resistive-inductive (C) resistive-capacitive (D) resistive-inductive-capacitive Answer: (D) resistive-inductive-capacitive 24 Series resonance will occur whenever a circuit's (A) resistance equals its reactance (B) reactance equals its impedance (C) inductive reatance equals its capacitive reactance

Answer: (C) inductive reatance equals its capacitive reactance 25 When series resonance occurs, the circuit's (A) resistance will equal its impedance (B) phase angle is zero (C) resistive voltage drop equals the supply voltage (D) each of the above Answer: (D) each of the above 26 At series resonance, if the circuit's resistance is significantly lower than its reactance, then the voltage drops appearing across the reactive components (A) will equal the supply voltage (B) may be significantly less than the supply voltage (C) may be significantly higher than the supply voltage Answer: (C) may be significantly higher than the supply voltage

Chapter 20 1

Energy' is defined as 'the (A) rate of doing work'.

(B) the ability to do work'.

(C) rate of transferring power'.

(D) mass multiplied by distance moved'.

Answer: (B) the ability to do work'.

2

Work' is defined as 'the (A) transfer of energy from a body at a higher temperature to one at a lower temperature', (B) transfer of energy from one form into another'.

(C) the rate of transferring power'.

Answer: (B) transfer of energy from one form into another'.

3

Heat' is defined as 'the (A) transfer of energy from a body at a higher temperature to one at a lower temperature', (B) thermal energy.

(C) the temperature of a body.

Answer: (A) transfer of energy from a body at a higher temperature to one at a lower temperature', 4

Power' is defined as 'the (A) rate of doing work'.

(B) rate of heat transfer'.

(C) rate of energy transfer'.

(D) any of the above.

Answer: (D) any of the above.

5

The SI unit of measurement for energy is the (A) watt.

(B) joule.

(C) kelvin.

(D) kilowatt hour.

Answer: (B) joule.

6

The SI unit of measurement for work is the (A) watt.

(B) joule.

(C) kelvin.

(D) kilowatt hour.

Answer: (B) joule.

7

The SI unit of measurement for heat is the (A) watt.

(B) joule.

(C) kelvin.

(D) kilowatt hour.

Answer: (B) joule.

8

The SI unit of measurement for power is the (A) watt.

(B) joule.

(C) kelvin.

(D) kilowatt hour.

Answer: (A) watt.

9

The rate at which energy is dissipated through heat transfer in an a.c. circuit is termed (A) apparent power'.

(B) true power'.

(C) reactive power'.

Answer: (B) true power'.

10 The above quantity is traditionally expressed in (A) watts.

(B) volt amperes.

(C) reactive volt amperes.

Answer: (A) watts.

11 The rate at which energy is alternately stored in a circuit's electric or magnetic field and returned to the supply, every quarter-cycle, is termed (A) apparent power'.

(B) true power'.

(C) reactive power'.

Answer: (C) reactive power'.

12 The above quantity is traditionally expressed in (A) watts.

(B) volt amperes.

(C) reactive volt amperes.

Answer: (C) reactive volt amperes.

13 The combination of the two quantities, described above, is termed the __________ of an a.c. circuit.

(A) apparent power'.

(B) true power'.

(C) reactive power'.

Answer: (A) apparent power'.

14 The above quantity is traditionally expressed in (A) volt amperes.

(B) reactive volt amperes.

(C) watts.

Answer: (A) volt amperes.

15 The apparent power of an a.c. load is the __________ of its true power and reactive power.

(A) algebraic sum.

(B) algebraic difference.

(C) vector sum.

(D) vector difference.

Answer: (C) vector sum.

16 To convert a voltage phasor diagram to a power diagram, (A) divide the voltage phasors by the reference phasor.

(B) multiply the voltage phasors by the reference phasor.

(C) add the reference phasor to the voltage phasors.

(D) subtract the reference phasor from the voltage phasors.

Answer: (B) multiply the voltage phasors by the reference phasor.

17 The term, 'power factor', is the (A) cosine of the phase angle.

(B) ratio of true power to apparent power.

(C) ratio of resistance to impedance.

(D) any of the above Answer: (A) cosine of the phase angle.

18 The term, 'leading' power factor, describes a circuit in which the (A) load current leads the supply voltage.

(B) load current lags the supply voltage.

(C) load current is in phase with the supply current.

Answer: (A) load current leads the supply voltage.

Chapter 21 1

The reference phasor for any a.c. circuit is normally drawn along the (A) positive horizontal axis.

(B) positive vertical axis.

(C) positive vertical axis.

(D) negative vertical axis.

Answer: (A) positive horizontal axis.

2

The reference phasor for a parallel a.c. circuit is the __________ phasor.

(A) supply voltage (B) current

Answer: (A) supply voltage 3

Phasors are said to 'rotate' (A) in a clockwise direction.

(B) in a counter-clockwise direction.

Answer: (B) in a counter-clockwise direction.

4

Dividing an a.c. parallel circuit's phasor diagram by the reference phasor will result in (A) an impedance diagram.

(B) an admittance diagram.

(C) a power diagram.

Answer: (B) an admittance diagram.

5

The reciprocal of resistance is called (A) admittance.

(B) susceptance.

(C) conductance.

(D) conductivity.

Answer: (C) conductance.

6

The reciprocal of impedance is called (A) admittance.

(B) susceptance.

(C) conductance.

(D) conductivity.

Answer: (A) admittance.

7

The SI unit of measurement for each of the above quantities is the (A) ohm.

(B) mho.

(C) siemens.

Answer: (C) siemens.

8

If a purely-resistive branch of a parallel circuit draws a current of 5 A when supplied with a voltage of 100 V, then its _________ must be __________.

(A) admittance, 20 mho (B) susceptance, 0.05 ohm.

(C) conductance, 0.05 siemens (D) conductivity, 20 siemens.

Answer: (C) conductance, 0.05 siemens 9

The admittance of a parallel a.c. circuit is the __________ its conductance and susceptance.

(A) difference between (B) algebraic sum of (C) vector sum of (D) vector difference between

Answer: (C) vector sum of 10 The phase angle of a parallel R-L circuit is the angle whose cosine is the ratio of (A) resistance to impedance.

(B) impedance to resistance.

(C) resistance to reactance.

(D) reactance to resistance.

Answer: (B) impedance to resistance.

11 The phase angle of a parallel R-L circuit is also equal to the angle whose cosine is the ratio of (A) conductance to admittance.

(B) admittance to conductance.

(C) conductance to susceptance.

(D) susceptance to conductance.

Answer: (A) conductance to admittance.

12 Multiplying an a.c. parallel circuit's phasor diagram by its reference phasor will result in (A) an impedance diagram.

(B) an admittance diagram.

(C) a power diagram.

Answer: (C) a power diagram.

13 The phase angle of a parallel a.c. circuit is the angle by which the ________ __________ the __________.

(A) supply voltage, leads or lags, load current (B) load current, leads or lags, supply voltage.

Answer: (B) load current, leads or lags, supply voltage.

14 The power factor of a parallel a.c. circuit is the ratio of (A) resistance to impedance.

(B) conductance to admittance.

(C) true power to apparent power.

(D) each of the above.

Answer: (D) each of the above.

Chapter 22 1

The power factor of a load is equal to the (A) sine of its phase angle.

(B) ratio of true power to apparent power.

(C) ratio of its resistance to reactance.

(D) each of the above.

Answer: (B) ratio of true power to apparent power.

2

Most industrial loads are __________ and, therefore, have ___________ power factors.

(A) resistive-inductive, lagging (B) resistive-inductive, leading (C) resisitive-capacitive, lagging (D) resistive-capacitive, leading

Answer: (A) resistive-inductive, lagging 3

Improving; or 'correcting' power factor means to change an existing power factor so that it (A) approaches unity.

(B) moves away from unity.

(C) increases beyond unity.

Answer: (A) approaches unity.

4

The effect of a 'poor' or low power factor is causes the load to (A) draw more energy than is necessary.

(B) operate below its power rating.

(C) draw more load current than necessary.

(D) operate less efficiently.

Answer: (C) draw more load current than necessary.

5

The greatest beneficiary of power-factor improvement is the (A) residential consumer.

(B) industrial consumer.

(C) the electricity network company.

(D) each of the above.

Answer: (C) the electricity network company.

6

The __________ derives absolutely no benefit whatsoever from power-factor improvement.

(A) residential consumer.

(B) industrial consumer.

(C) the electricity network company.

Answer: (A) residential consumer.

7

The most common method of power-factor improvement is by connecting a suitable capacitor (A) in series with the load.

(B) in parallel with the load.

(C) in series or in parallel with the load.

Answer: (B) in parallel with the load.

8

When a capacitor is connected to improve power factor, the current drawn by the load __________, while the current drawn from the supply __________.

(A) increases, reduces (B) reduces, remains the same (C) increases, remains the same.

(D) remains the same, reduces

Answer: (D) remains the same, reduces 9

Power-factor correction capacitors are usually rated in (A) microfarads.

(B) watts.

(C) reactive volt amperes.

(D) volt amperes.

Answer: (C) reactive volt amperes.

10 The main incentive for industrial consumers to improve the power factor of their loads is (A) a reduction in the energy they consume.

(B) any motors will run more efficiently.

(C) they will not be subject to penalty surcharges.

(D) their loads draw less current.

Answer: (C) they will not be subject to penalty surcharges.

11 It is rarely economical for an industrial consumer to improve the power factor of their load to unity because (A) of the capital cost of the necessary power-factor correction equipment.

(B) their loads are not constant.

(C) the cost of energy varies over time.

Answer: (A) of the capital cost of the necessary power-factor correction equipment.

Chapter 23 1

The main reason why electricity transmission and distribution as three-phase a.c. is because (A) for a given load, it is more economical than single phase.

(B) the voltage drops along single-phase lines are excessively high.

(C) it is essential in order to maintain a balanced load.

Answer: (A) for a given load, it is more economical than single phase.

2

Another advantage of three-phase systems, over single-phase systems, is (A) smoother energy delivery.

(B) three-phase motors are self-starting.

(C) three-phase machines are smaller, lighter, and more efficient.

(D) each of the above.

Answer: (D) each of the above.

3

The voltages generated by a three-phase generator are displaced from each other by __________ electrical degrees.

(A) 30 (B) 60 (C) 90 (D) 120

Answer: (D) 120 4

The order in which of these generated voltages each reach their maximum values is termed their (A) synchronization.

(B) phase sequence.

(C) phase displacement.

(D) phase rotation.

Answer: (B) phase sequence.

5

The three energised conductors that connect a three-phase supply to its load are termed (A) phase conductors.

(B) line conductors.

(C) transmission conductors.

(D) distribution conductors.

Answer: (B) line conductors.

6

A three-phase connection, in which the end of one the windings is connected to the start of the next, is called a (A) star' or 'wye' connection.

(B) delta' or 'mesh' connection.

Answer: (B) delta' or 'mesh' connection.

7

A three-phase connection, in which there is a common point of connection between all three windings, is called a (A) star' or 'wye' connection.

(B) delta' or 'mesh' connection.

Answer: (A) star' or 'wye' connection.

8

The common point of connection, described in the previous question, is called the windings' (A) star point'.

(B) neutral point', (C) either above.

Answer: (C) either above.

9

The voltage measured directly across any one of the three-phase windings or loads is called a (A) phase voltage.

(B) line voltage.

Answer: (A) phase voltage.

10 The voltage measured directly between any pair of the three energised conductors connecting a three-phase supply to its load is called a (A) phase voltage.

(B) line voltage.

Answer: (B) line voltage.

11 When we refer to a '400-kV' transmission line, or an '11-kV distribution line', we are describing their (A) phase voltages.

(B) line voltages.

Answer: (B) line voltages.

12 The current flowing within each winding or load of a three-phase system is called a (A) load current.

(B) branch current.

(C) phase current.

(D) line current.

Answer: (C) phase current.

13 The current flowing in the neutral of a star-connected load is (A) always zero.

(B) the algebraic sum of the three line currents.

(C) the phasor sum of the three line currents.

(D) the difference between the three line currents.

Answer: (C) the phasor sum of the three line currents.

14 For a delta-connected supply, the line voltage is __________ times the phase voltage.

(A) 0.707 (B) 1 (C) 1.414 (D) 1.732 Answer: (B) 1 15 For a star-connected supply, the line voltage is __________ times the phase voltage.

(A) 0.707 (B) 1 (C) 1.414 (D) 1.732 Answer: (D) 1.732 16 For a balanced delta-connected load the line current is __________ times the phase current.

(A) 0.707 (B) 1 (C) 1.414 (D) 1.732 Answer: (D) 1.732 17 For a balanced star-connected load the line current is __________ times the phase current.

(A) 0.707 (B) 1 (C) 1.414 (D) 1.732 Answer: (B) 1 18 For a balanced star-connected load, the neutral current is __________.

(A) zero (B) one-third of the sum of the three line currents.

(C) the sum of the three line currents.

(D) 1.732 times any one of the line currents.

Answer: (A) zero 19 In three-phase systems, the three __________ are identified in various ways, including using letters (A-B-C), numerals, (1-2-3), etc.

(A) phases (B) lines Answer: (B) lines 20 Using 'double-subscript notation', UAB is read as meaning (A) voltage A-B'.

(B) the potential at A with respect to B'.

(C) the potential at B with respect to A'.

Answer: (B) the potential at A with respect to B'.

21 Using 'double-subscript notation', IA is read as meaning (A) the current in line A'.

(B) the current in phase A'.

Answer: (A) the current in line A'.

22 Under the EU harmonisation rules, three-phase systems use the following identification colours: (A) red-yellow-blue.

(B) red-white-blue.

(C) brown-black-grey.

(D) brown-black-orange.

Answer: (C) brown-black-grey.

23 When constructing a three-phase phasor diagram, it is usual for it to apply to the __________, not the __________.

(A) load, supply (B) supply, load Answer: (A) load, supply 24 When constructing a three-phase phasor diagrem, it is usual to construct the phasors in the following sequence: (A) phase voltage, phase current, line voltage, line current.

(B) line voltage, line current, phase voltage, phase current (C) phase voltage, line voltage, phase current, line current.

(D) phase current, line current, phase voltage, line voltage.

Answer: (C) phase voltage, line voltage, phase current, line current.

25 When constructing a three-phase phasor diagram, the reference phasor is usually taken as the (A) phase voltage.

(B) line voltage.

(C) phase current.

(D) line current.

Answer: (A) phase voltage.

26 For a balanced three-phase load, the total power is equal to (A) the square-root of 3 multiplied by the power of any one phase.

(B) three times the power of any one phase.

Answer: (B) three times the power of any one phase.

27 For a balanced three-phase load, the total power is equal to (A) 3 x line voltage x line current (B) 3 x line voltage x line current x power factor (C) 3 x phase voltage x phase current (D) 3 x phase voltage x phase current x power factor Answer: (D) 3 x phase voltage x phase current x power factor 28 For a balanced three-phase load, the total power is equal to (A) root 3 x line voltage x line current (B) root 3 x line voltage x line current x power factor (C) root 3 x phase voltage x phase current (D) root 3 x phase voltage x phase current x power factor Answer: (B) root 3 x line voltage x line current x power factor 29 The secondary of a star-connected transformer supplies a balanced, delta-connected load. If the nominal phase voltage of the supply is 230 V, then the phase voltage of the load is approximately: (A) 133 V. (B) 230 V. (C) 400 V. Answer: (C) 400 V. 30 In the above example, if the load has a phase current of 15 A, then the phase current of the supply must be approximately (A) 8.67 A. (B) 15 A. (C) 26 A.

Answer: (C) 26 A.