Electricity & CircuitsEdexcel GCSE Physics: Topic test

20 questions, 54 marks

Edexcel GCSE Physics

Electricity & Circuits topic test

Total 54 marks

Name

Class

Date

1
A phone charger provides a constant current of 2 A to charge a phone's battery for 3 minutes. The charging cable itself acts as a small resistor of resistance 0.5 Ω, so there is a potential difference across the cable while the current flows.
(a)
What is an electric current, in terms of charge?
[1 mark]
AThe rate of flow of electric charge
BThe energy transferred by charge each second
CThe force needed to move charge along a wire
DThe potential difference across a component
(b)
What potential difference is there across the charging cable while the 2 A current flows through its 0.5 Ω resistance?
[1 mark]
A2.5 V
B1 V
C0.25 V
D4 V
(c)
Calculate the charge that flows through the phone's battery during the 3 minutes (180 s) of charging at a constant current of 2 A.
[2 marks]
Total for question 1: 4 marks
2
A student builds two circuits using the same battery and two identical lamps, P and Q. In circuit 1, lamp P and lamp Q are connected in series with the battery. In circuit 2, the same two lamps are instead connected in parallel with each other, then connected to the same battery.
(a)
Compared with circuit 1, how does the brightness of each lamp in circuit 2 compare, and why?
[1 mark]
AEach lamp is dimmer in circuit 2, because the total circuit resistance has increased
BEach lamp is equally bright in both circuits, because the lamps are identical
CEach lamp is brighter in circuit 2, because each lamp now has the full battery potential difference across it rather than a shared share of it
DEach lamp is brighter in circuit 2, because parallel circuits always reduce resistance to zero
(b)
If lamp P in circuit 1 (the series circuit) blows and stops conducting, what happens to lamp Q?
[1 mark]
ALamp Q stays lit at the same brightness, because it is a separate component
BLamp Q becomes brighter, because all the current now flows through it alone
CLamp Q flickers randomly until the circuit is fixed
DLamp Q also goes out, because the circuit is now broken and no current can flow
(c)
State what would happen to lamp Q in circuit 2 (the parallel circuit) if lamp P blew instead, and explain why this differs from the series case.
[2 marks]
Total for question 2: 4 marks
3
An electric heater transfers 1200 J of energy every 4 seconds when connected to the 230 V mains supply.
(a)
Calculate the power of the heater, and then calculate the current it draws from the 230 V supply.
[3 marks]
(b)
Explain, in terms of electrons and the lattice of ions in the heating element, why the heater becomes hot when this current flows through it, and explain one way the connecting wires leading to the heater could be designed to reduce unwanted energy losses.
[4 marks]
Total for question 3: 7 marks
4
A construction worker uses a portable circular saw on a building site. The saw is connected to a generator's 230 V, 50 Hz a.c. supply through a cable fitted with a residual current device (RCD) and a standard plug containing a 13 A fuse and an earth pin connected to the saw's metal casing.
(a)
Explain the function of the earth wire and the fuse in this circuit, describing what happens if a fault causes the saw's metal casing to become connected to the live wire.
[6 marks]
(b)
The RCD provides additional protection beyond the fuse and earth wire. Explain how an RCD works to protect the worker, and explain, in terms of energy transfer, why gripping a faulty live tool for even a very short time can still be dangerous, even though the RCD disconnects the supply very quickly.
[6 marks]
Total for question 4: 12 marks
5
A student checks that a torch bulb rated for a maximum current of 0.3 A is protected when used with a 9 V supply. She connects the bulb in series with a fixed protective resistor of resistance 25 Ω, a switch, an ammeter and the 9 V battery.
(a)
Which piece of apparatus should be connected in series with the bulb to measure the current in it?
[1 mark]
AAn ammeter
BA voltmeter
CAn ohmmeter
DA galvanometer connected in parallel
(b)
The circuit is a single loop with the bulb, resistor, ammeter, switch and battery. If the ammeter reads 0.28 A, what is the potential difference across the 25 Ω protective resistor?
[1 mark]
A8.93 V
B7 V
C0.0112 V
D25.28 V
(c)
The battery supplies 9 V in total. Given the potential difference across the resistor is 7 V (from part b), calculate the potential difference across the bulb, and state the rule you used.
[2 marks]
Total for question 5: 4 marks
6
A workshop's inspection lamp uses two identical lamps, X and Y. A technician first tests lamp X alone in a circuit connected to a 12 V supply, where it draws a current of 0.5 A. She then adds lamp Y in parallel with lamp X, keeping the same 12 V supply.
(a)
What happens to the total resistance of the circuit when lamp Y is added in parallel with lamp X?
[1 mark]
AIt increases, because there are now more components
BIt stays the same, because the lamps are identical
CIt decreases, because parallel branches provide additional paths for current to flow
DIt becomes infinite, because a short circuit is created
(b)
What happens to the total current drawn from the 12 V supply once lamp Y is added in parallel?
[1 mark]
AIt decreases, since more resistance is added
BIt stays exactly at 0.5 A, since lamp X is unaffected
CIt becomes zero, since the circuit is now broken
DIt increases, since each lamp still draws its own current from the same p.d. and the branch currents combine
(c)
Lamp Y, being identical to lamp X, also draws 0.5 A when 12 V is across it. Calculate the total current drawn from the supply once both lamps are connected in parallel, and state the rule you used.
[2 marks]
Total for question 6: 4 marks
7
An electric drill motor is rated at 750 W when connected to the 230 V mains supply and is used continuously for 10 minutes (600 s).
(a)
Calculate the current drawn by the drill motor, and the total energy it transfers in the 600 seconds of use.
[3 marks]
(b)
The drill becomes noticeably warm to the touch after continuous use, even though it is designed mainly to do mechanical work turning the drill bit. Explain, in terms of energy transfers, why the drill's casing heats up during use, and suggest one design feature that could reduce this unwanted heating without reducing the drill's cutting performance.
[4 marks]
Total for question 7: 7 marks
8
A farmer installs an electric fence controller in a barn, connected to the 230 V, 50 Hz a.c. mains supply through a plug wired with live, neutral and earth wires and a 3 A fuse. The controller's metal control box is connected to the earth pin, and the controller normally draws an operating current of 1.2 A.
(a)
Explain what is meant by an alternating current supply, and explain why the controller's fuse is rated at 3 A when the controller itself is designed to safely draw a normal operating current of only 1.2 A.
[6 marks]
(b)
The controller delivers short, high-voltage pulses to the fence wire using energy stored and released by components inside the box. Explain why the earth wire connected to the metal control box is an important safety feature, and, referring to Q = I × t, explain why a fault current flowing to earth for even a fraction of a second can still be enough to blow the fuse and disconnect the supply.
[6 marks]
Total for question 8: 12 marks

End of questions