AQA GCSE Physics Grade6/7 Booster Workbook

Section 2: Electricity

Circuit diagrams 1.

Identify the circuit symbols in Table 1. +

symbol

+

name Table 1 2.

[4 marks]

Complete Table 2 by drawing the circuit symbols. symbol name

fixed resistor

variable resistor

ammeter

Table 2 3.

[3 marks]

Draw a circuit showing a cell and three lamps, each of which can be switched on and off independently.

[2 marks]

Electrical charge and current Worked Example

2.0 C of charge flows through a resistor in 50 s.

Calculate the current through the resistor.

Give your answer in mA.

[4 marks]

Using the equation Q = It 2.0 = I × 50

Remember You need to learn the equation relating charge flow to current and time as it may not be given to you in the exam.

[1 mark]

This can be rearranged to give I=

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[1 mark]

= 0.040 A

[1 mark]

= 40 mA

[1 mark] 17

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1.

+

An electric circuit is shown in Figure 1. a Write down the equation that links charge flow,

current and time.

A Figure 1

Maths Skills

[1 mark]

C

[2 marks]

b The ammeter reads 0.020 A.

Calculate the charge that flows through the lamp in 100 s.

Maths Skills

Charge =

c The variable resistor is now adjusted so that the lamp becomes much dimmer.

It takes 100 s for 1.2 C to pass through the lamp.

Calculate the current through the lamp.

Give your answer in mA.

2.

mA

Current =

[4 marks]

The reading on the ammeter in the circuit in Figure 2 is 200 μA. Remember

A

Maths Skills

The size of an electric current is sometimes expressed in microamps (μA). ‘micro’ is a prefix which is equal to 10001 000 . So 1 μA = 1 × 10−6 A.

+

Figure 2

Calculate the time taken for 1.0 C of charge to pass through the resistor.

Time =

s

[4 marks]

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2

Electrical resistance Worked Example

The potential difference across a 120 Ω resistor is 6.0 V. Calculate the current flowing through the resistor.

Give your answer in mA.

[4 marks]

Remember You need to learn the equation linking potential difference, current and resistance as it may not be given to you in the exam.

Using the equation V = IR 6.0 = I × 120 I=

1.

Maths Skills

[1 mark]

= 0.050 A

[1 mark]

= 50 mA

[1 mark]

6.0 120

In a circuit, the potential difference across a 200 Ω resistor is 9.0 V. Calculate the current through the resistor.

Give your answer in mA.

2.

Maths Skills

[1 mark]

Current =

When the switch in the circuit in Figure 3 is closed the ammeter reads 60 mA and the voltmeter reads 1.5 V.

mA

[4 marks]

+

Calculate the resistance of resistor R.

A R V

Resistance =

Ω

[4 marks]

Figure 3

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3.

a A student is asked to determine the combined resistance of two unknown resistors

connected in series as shown in Figure 4.

Required practical

Figure 4

Draw on Figure 4 the circuit that the student could use to determine the value of the combined resistance.

[3 marks]

b Describe how the student should use the equipment in the circuit to determine the

value of the combined resistance.

4.

Required practical

[2 marks]

A student uses the circuit shown in Figure 5 to investigate how the resistance of a wire depends on its length.

Before starting the investigation, the student made the following prediction: The resistance of the wire will be directly proportional to its length. +

a The student measured the resistance of eight different

A

lengths of wire.

All eight lengths had the same diameter.

Explain why it is important that the wires had the same diameter.

X

wire

Y

V Figure 5

[2 marks]

20

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2 b Explain why it is important to make sure there are no kinks in the wire.

[1 mark]

c Identify the dependent, independent and control variables.

Dependent variable:

Independent variable:

Control variable:

[3 marks]

d The graph shows the student’s values of resistance for each of the eight lengths of wire.

The student has drawn a line of best fit.

6.0

Resistance ( )

5.0 4.0 3.0 2.0 1.0 0 0

0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 Length (m)

Figure 6

Give the range of lengths that the student used.

[1 mark]

e Explain why the data plotted in Figure 6 supports the student’s prediction.

[1 mark]

f Use the graph to predict the length of wire that would have a resistance of 1.6 Ω.

Length =

m

[1 mark]

g The gradient of the graph is equal to the resistance per metre of the wire.

Determine the resistance per metre of the wire.

Gradient =

Ω/m

[1 mark]

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