Final Revision A) Choose the correct answer from those between brackets 1. If the length of a resistor is doubled and its cross-sectional area is decreased to half, then its resistance becomes ………….. a. Double its value c. Fixed b. 4 times its value d. 8 times its value 2. If the E.M.F. of a cell equals 10 volts, its terminal voltage when a current is flowing through its circuit equals………… a. 10 volt b. less than 10 volt c. greater than 10 volt 3. Two resistors are connected in parallel. One of them equals 1 ohm. Their equivalent resistance is …………….1 ohm. a. greater than b. equal to c. smaller than 4. In the electric circuit shown in the figure, if the reading of the ammeter (A1) was 6 ampere then the reading of the ammeter (A2) equal ………. ampere a. 2 b. 4 c. 6 d. 8 5. In the electric circuit shown in the figure. If the reading of the ammeter (A) is 4 ampere and the current passing through the resistance R1 is 1 ampere then the value of the resistance R2 is…….. ohm a. 2 b. 4 c. 6 d. 8
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6. From the circuit given in the figure, the reading of voltmeter is ………... volt, if reading of ammeter is 1 ampere. a. 4 b. 8 c. 12 d. 18 7. In the previous electric circuit if the internal resistance of the battery negligible, then e.m.f of the battery equal ……… volt a. 6 c. 24 b. 12 d. 30 8. The torque acting on a coil carrying a current in a uniform magnetic field becomes maximum when the plane of the coil is…………. the direction of the magnetic field. a. parallel to c. inclined by an angle 30° to b. Perpendicular to d. inclined by an angle 60° to 9. The concave magnetic poles in the moving coil galvanometer make the magnetic flux lines in the shape of………… a. straight lines c. radial b. circles d. curved 10. The moving coil galvanometer is used to measure the potential difference when its coil connected with a …………….. a. small resistance on parallel c. large resistance on parallel b. small resistance on series d. large resistance on series 11. Eddy currents are useful in designing ………….. a. electric transformer c. Ruhmkorff coil b. electric generator d. induction furnace 12. The density of the magnetic field is measured by the unit:……… a. Weber/second c. Volt/meter b. Coulomb/kilogram d. Newton/Amp.meter 13. The average value of the current intensity (I) of the A.C. current through complete cycle equals: ……………….. a. Ieff c. zero b. Imax d. there is no correct answer 2 | Page (Revision)
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14. Capacitor its capacitance is connected to a non-inductive ohmic resistance of 1000 , if an AC current of frequency 500 Hz passing through it therefore :a. The total impedance equals ………. i. 1414.2 iii. ii. 1000 iv. b. Voltage lags current by phase angle equals ……….. i. 50 iii. 90 ii. 45 iv. 63.75 15. At resonance circuit, the phase angle between current and voltage equals ………….. a. 90 c. 180 b. 270 d. 0 16. A dynamo coil of neglected internal resistance is connected to capacitor, if the rotation frequency of the dynamo increases to double, the capacitive reactance of capacitor will be……….. a. decrease to half c. decrease four times b. increase to double d. fixed 17. A 1 mH inductor and 10 µF capacitor connected in series to an AC source possess equal reactance. The angular velocity of this AC source is………rad/sec. a. 104 c. 10 b. 100 d. 200π 18. If the internal resistance of the battery is negligible in the shown electric circuit and an ammeter (A) reads 4 A when the switch is open. The reading on the ammeter (A1) when the switch is closed will be………….ampere a. 1 b. 2 c. 3 d. 4
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19. Two straight parallel wires (A and B) carry electric currents 1 A and 2 A. If the force acting on the wire (A) is F, so the force acting on the wire (B) is……….. c. a. d. b. 20. A transformer has an input DC voltage of 110 volts, a primary coil of 100 turns and a secondary coil of 10 turns. What is its output voltage?............. a. 55V c. 220V b. 110V d. Zero 21. An electric circuit consists of AC source 28V, inductive coil of inductive reactance 12 Ω and negligible ohmic resistance and a capacitor of capacitive reactance 16 Ω so the current in the circuit is ……. a. zero c. 7A b. 1A d. 1.4A 22. When a resistance R is connected to an ohmmeter of resistance 2400 Ω , the pointer deflects to quarter of the current scale. So the value of R is ………. a. 2400 Ω c. 7200 Ω b. 4800 Ω d. 9600 Ω 23. If a circular coil re-wrapped such that its turns increases 3 times, allowing the same current to pass through it, the magnetic flux density at its center ………. a. increases 3 times c. increases 9 times b. increases 6 times d. does not change 24. Which of the following quantities increases in the secondary coil of an ideal step down transformer when its primary coil is connected to AC source? ………………… a. electric power b. current frequency c. effective value of current d. effective value of voltage
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25. Which diagram represents the vectors of the total voltage and the current in a circuit consisting of an inductor, an ohmic resistance and an AC supply?..............
26. When two resistors R and 4 R are connected in parallel to a battery. The consumed power in the resistor R is …….. that consumed in the resistor 4R. a. 4 times c. equal to b. double d. A quarter of 27. The scale of a sensitive galvanometer consists of 20 divisions. Its pointer deflects to half scale when a current of intensity 0.1 milli-ampere passes through its coil. The device sensitivity equals……… a. 20 microampere/division c. 5 microampere/division b. 10 microampere/division d. 2 microampere/division 28. When the phase angle between the total voltage and the current in (LCR) circuit = zero, the ratio = ………. a. zero c. 0.5 b. 1 d. 2 29. Direction of magnetic dipole moment is determined from ………. a. right hand screw rule c. Fleming’s left hand rule b. Fleming’s right hand rule d. Lenz’s rule 30. The ratio between the energy of the photon and the light velocity in air is the ………….of the photon a. mass b. linear momentum c. frequency d. kinetic energy
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31. In the opposite circuit, I2 = ………… a. 5 A b. 10 A c. 15 A d. 20 A 32. In the opposite circuit: XL = R, when a current frequency (f) passing through the circuit and if the frequency is increased to (3f) , the ratio between the impedance before and after increasing the frequency becomes ……….. a. b. c.
√ √ √ √
d. 33. In the shown figure at closing switch K1, the sensitivity of device decreases to its quarter so, the ratio between the sensitivity of the device and the galvanometer when closing the two switches together is ……….. a. b. c. d. 34. The ratio between the kinetic energy and its velocity is ………. a. c. b.
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d.
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35. In the opposite electric circuit: the ratio between the quantity of charge on plate C1 and C3 is ……………… a. b. c. d. 36. AC circuit contains a resistance R, capacitor C and coil L which are connected in series so, the potential difference VC …………. a. leads VR by 90° c. lags by VL by 180° b. lags VR by 180° d. lags by VR by 45° 37. The slope of the straight line which represents the relation between the photon’s energy and its frequency equals ………… a. wavelength c. light velocity b. Planck’s constant d. linear momentum 38. The resonant circuits are used in ……….. a. generation of mechanical c. remote sensing waves d. all the previous b. wireless devices 39. The opposite figure represents the graphical relation between the potential difference between poles of two electric cells (A,B) and the electric current intensity passing through the circuit of each of them, so the relation between their internal resistances = ………… a. b. c.
√
d. √
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40. The ratio of the frequencies of two photons are 1: 3, so the ratio between their energies is ………… a. 1 : 3 c. 3 : 1 b. 1 : 1 d. 1 : 6 41. In the opposite figure, if the potential at points B,C,D are 2V,12V,18V respectively, then:a. The potential at point A is ………… i. 4V ii. 8V iii. 12V iv. 16V b. The potential difference between A and B is ……….. i. 6 V iii. 14 V ii. 10 V iv. 20 V 42. In the opposite figure if the potential difference between (x , y) is quarter the potential between (z, y), then the value of R is ……….. a. 5 Ω b. 10 Ω c. 20 Ω d. 40 Ω 43. In the electric circuit shown in the figure, if the reading of the ammeter while switch K is open is 1.5 A, then the reading of voltmeter when the switch is closed equals ………… a. 4 V b. 8 V c. 1 V d. 12 V
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44. The opposite figure illustrates the graphical relation between each of the potential difference and current on the vertical axis and the time on the horizontal axis, so the generated power equals ……… a. 50 W b. 125 W c. 250 W d. 500 W 45. The opposite figure shows a coil placed in a magnetic field where it is cut by a magnetic flux . In which of the following cases a magnetic flux of cuts the coil? ……………
46. The opposite graph illustrates the relation between the magnetic flux that cuts a dynamo’s coil and the angle between the plane of the coil and field within half cycle. If the number of turns of the coil 100 turns and it rotates in the rate of 60 cycle per second, the average generated emf within a three-quarter cycle equals……………. a. 100 c. 300 b. 200 d. 400
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