Free D.C. circuits questions for AS Level Physics (9702), part of Waves, electricity & particles. Each question has the answer and the marking points an examiner would look for.
Generate a full D.C. Circuits worksheet →All Waves, electricity & particles questionsA potentiometer wire of length 80.0 cm has a constant p.d. of 1.5 V across it. A cell of e.m.f. 1.20 V is connected so that it can be balanced against part of the wire.
What is the balance length?
Answer: C
What happens to the terminal p.d. of a battery as the current drawn increases?
Answer: D
Which statement describes Kirchhoff’s first law?
Answer: A
A battery of e.m.f. 6.0 V and internal resistance 1.5 Ω is connected to a resistor of 6.0 Ω.
Explain, in terms of energy, the difference between e.m.f. and potential difference.
Calculate the terminal p.d. and the efficiency of the circuit.
A thermistor is connected in series with a fixed resistor of 2000 Ω across a 9.0 V supply of negligible internal resistance. The thermistor resistance is 4000 Ω at 10 °C and 1000 Ω at 40 °C. Calculate the change in the p.d. across the fixed resistor as the temperature rises from 10 °C to 40 °C.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | e.m.f.: energy converted from other forms to electrical per unit charge; p.d.: electrical energy converted to other forms per unit charge e.m.f.: other forms → electrical, per unit charge B1 p.d.: electrical → other forms, per unit charge B1 | 2 |
| (b) | 4.8 V, 80% I = 0.8 A C1 V = 4.8 V A1 80% A1 | 3 |
| (c) | 3 V increase potential divider formula C1 3.0 V and 6.0 V C1 increase of 3.0 V A1 | 3 |
A potentiometer circuit is used to compare e.m.f.s.
Explain why a potentiometer measures the e.m.f. of a cell rather than its terminal p.d. at the balance point.
| Part | Answer and marking points | Marks |
|---|---|---|
| no current drawn from cell at balance there is no current in the cell B1 so there is no p.d. across its internal resistance B1 | 2 |
A battery of e.m.f. 6.0 V and internal resistance 2.0 Ω is connected to two resistors of 6 Ω and 12 Ω in parallel.
Define e.m.f. and distinguish it from potential difference.
Calculate the current in the battery.
Use your answer to (b) to calculate the terminal p.d. of the battery.
State Kirchhoff’s first law and explain which conservation law it is based on.
Calculate the fraction of the total power from the battery that is dissipated in the internal resistance.
| Part | Answer and marking points | Marks |
|---|---|---|
| (a) | energy transferred from other forms to electrical per unit charge; p.d.: electrical to other forms per unit charge e.m.f.: energy transformed from other forms to electrical energy per unit charge B1 p.d.: electrical energy transformed to other forms per unit charge B1 | 2 |
| (b) | 1.00 A parallel R = 4.00 Ω C1 I = E/(R + r) C1 1.00 A A1 | 3 |
| (c) | 4.00 V V = E − Ir = 4.00 V B1 | 1 |
| (d) | sum of currents into junction = sum out; conservation of charge sum of currents into a junction equals sum of currents out B1 conservation of charge B1 | 2 |
| (e) | 0.333 Pr/Ptotal = I2r/(EI) = r/(R + r) C1 0.333 A1 | 2 |
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Meet Riyaz →Original Cambridge-style practice questions written for mentorriyaz.in. These are not Cambridge past paper questions, and this site is not affiliated with or endorsed by Cambridge University Press & Assessment. Updated 2026-11-04. Paper generator · mentorriyaz.in