Electric CircuitsEdexcel International A Level Physics: Topic test

20 questions, 54 marks

Edexcel International A Level Physics

Electric Circuits topic test

Total 54 marks

Name

Class

Date

1
A phone charger supplies a steady current of 1.5 A at a p.d. of 5.0 V to a phone for 40 minutes. The charge on an electron is 1.60 × 10⁻¹⁹ C.
(a)
How much charge passes through the phone in this time?
[1 mark]
A3600 C
B60 C
C1600 C
D6.3 × 10⁻⁴ C
(b)
How much electrical energy is transferred to the phone in this time?
[1 mark]
A720 J
B3.6 kJ
C18 kJ
D300 J
(c)
Calculate the number of electrons that pass through the phone each second.
[2 marks]
Total for question 1: 4 marks
2
A 10 V supply of negligible internal resistance is connected to an 8.0 Ω resistor in series with two resistors in parallel, of resistance 30 Ω and 20 Ω.
(a)
What is the total resistance of the circuit?
[1 mark]
A58 Ω
B20 Ω
C12 Ω
D0.050 Ω
(b)
What is the current in the 30 Ω resistor?
[1 mark]
A0.50 A
B0.30 A
C0.33 A
D0.20 A
(c)
The current in the 8.0 Ω resistor is 0.50 A. Use Kirchhoff's second law to show that the p.d. across the parallel pair is 6.0 V.
[2 marks]
Total for question 2: 4 marks
3
A resistor of resistance 470 Ω has a maximum power rating of 0.25 W.
(a)
Calculate the largest p.d. that can be applied across the resistor without exceeding its power rating.
[3 marks]
(b)
Two resistors identical to this one are connected in series across a 24 V supply of negligible internal resistance. Determine whether either resistor exceeds its power rating.
[4 marks]
Total for question 3: 7 marks
4
An aluminium power cable has a diameter of 12 mm and carries a steady current of 100 A. For aluminium, the number density of conduction electrons is 1.8 × 10²⁹ m⁻³ and the resistivity is 2.8 × 10⁻⁸ Ω m. The charge on an electron is 1.60 × 10⁻¹⁹ C.
(a)
Calculate the drift speed of the conduction electrons in the cable and the resistance of a 1.0 km length of the cable.
[6 marks]
(b)
A designer claims that using a cable of the same aluminium with twice the diameter would halve the power wasted as heat in a 1.0 km length carrying the same current. Evaluate this claim.
[6 marks]
Total for question 4: 12 marks
5
A 12 V supply of negligible internal resistance is connected across a 100 Ω uniform resistance track, forming a potential divider. A sliding contact is set at a point 25 Ω of track away from the negative end, and the output is taken between the sliding contact and the negative end.
(a)
What is the output p.d. when nothing is connected to the output?
[1 mark]
A0.48 V
B9.0 V
C3.0 V
D6.0 V
(b)
A 100 Ω load resistor is now connected across the output. What is the new output p.d.?
[1 mark]
A3.0 V
B2.4 V
C3.6 V
D2.5 V
(c)
The output is to be set to exactly 4.0 V with nothing connected to it. Calculate the resistance of the section of track between the sliding contact and the negative end.
[2 marks]
Total for question 5: 4 marks
6
A car battery has an e.m.f. of 12.6 V and an internal resistance of 0.030 Ω. It is connected to a starter motor, which can be treated as a resistor of resistance 0.060 Ω.
(a)
What current is drawn from the battery?
[1 mark]
A140 A
B210 A
C420 A
D7.1 × 10⁻³ A
(b)
What is the terminal p.d. of the battery while the starter motor is running?
[1 mark]
A4.2 V
B8.4 V
C12.6 V
D17 V
(c)
As the battery ages, its internal resistance increases. Explain the effect on the terminal p.d. while the starter motor is running.
[2 marks]
Total for question 6: 4 marks
7
An NTC thermistor of resistance 40 Ω at 20 °C is connected in series with a heating element of resistance 8.0 Ω across a 12 V supply of negligible internal resistance. The current warms the thermistor until its resistance has fallen to 4.0 Ω.
(a)
Calculate the current in the circuit, and the p.d. across the heating element, at the start and after the thermistor has warmed.
[3 marks]
(b)
Explain, in terms of conduction electrons and lattice vibrations, why the current increases as the thermistor warms.
[4 marks]
Total for question 7: 7 marks
8
A 9.0 V battery of internal resistance 3.0 Ω is used to light an LED through a protective series resistor R. When the LED is lit, the current in the circuit is 20 mA and the p.d. across the LED is 2.0 V.
(a)
Calculate the resistance of R.
[6 marks]
(b)
A technician suggests using a resistor with a power rating of 0.125 W for R. Evaluate this suggestion and calculate the percentage of the battery's power that is transferred to the LED.
[6 marks]
Total for question 8: 12 marks

End of questions

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).