AS Level Physics chapter 9: Electricity MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

74 exam-style questions on Electricity, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

74 questions · 3 topics · 10 per test

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What chapter 9 covers

Ten Electricity questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. The p.d. across a component is 12 V and a charge of 5.0 C passes through it. How much energy is transferred?

  1. A
    2.4 J
  2. B
    17 J
  3. C
    60 J
  4. D
    0.42 J
Show answer

Answer: C. W = QV = 5.0 × 12 = 60 J. The volt is a joule per coulomb.

2. The potential difference across a resistor is 6.0 V. Which statement is correct?

  1. A
    6.0 J of energy is transferred in the resistor every second
  2. B
    6.0 C of charge passes through the resistor every second
  3. C
    each electron passing through the resistor transfers 6.0 J of energy
  4. D
    6.0 J of energy is transferred in the resistor for each coulomb of charge that passes through it
Show answer

Answer: D. 6.0 V means 6.0 J per coulomb. The energy per second depends on the current too, and one electron (charge 1.6 × 10−19 C) transfers only 9.6 × 10−19 J.

3. Potential difference is energy transferred per unit charge. What are the SI base units of potential difference?

  1. A
    kg m2 s−1 A−1
  2. B
    kg m2 s−2 A−1
  3. C
    kg m2 s−3 A−1
  4. D
    kg m s−3 A−1
Show answer

Answer: C. J = kg m2 s−2 and C = A s, so V = J/C = kg m2 s−3 A−1. Writing the coulomb as A instead of A s gives s−2.

4. The I–V characteristic of a filament lamp is plotted for p.d.s from −6 V to +6 V, with current on the vertical axis. Which describes the part of the graph for negative p.d.s?

  1. A
    the current is zero for all negative p.d.s
  2. B
    a straight line through the origin, because the lamp is cold in reverse
  3. C
    a curve whose gradient increases as the p.d. becomes more negative
  4. D
    a curve whose gradient decreases as the p.d. becomes more negative, so the graph has rotational symmetry about the origin
Show answer

Answer: D. A lamp behaves the same whichever way the current flows: the filament heats up and its resistance rises in both directions. The negative half is the positive half rotated through 180° about the origin. Zero current in reverse describes a diode.

5. A phone battery is rated at 3000 mA h. How much charge can it deliver when fully charged?

  1. A
    3.0 C
  2. B
    180 C
  3. C
    3000 C
  4. D
    10 800 C
Show answer

Answer: D. Q = It = 3.0 A × 3600 s = 10 800 C. 1 mA h is 1 mA flowing for one hour.

6. A wire of cross-sectional area 2.0 mm2 carries a current of 4.0 A. The drift speed of the free electrons is 1.0 × 10−4 m s−1. What is the number density of free electrons? (e = 1.60 × 10−19 C)

  1. A
    8.0 × 10−30 m−3
  2. B
    1.3 × 1023 m−3
  3. C
    1.3 × 1026 m−3
  4. D
    1.3 × 1029 m−3
Show answer

Answer: D. 2.0 mm2 = 2.0 × 10−6 m2. n = I/(Avq) = 4.0 ÷ (2.0 × 10−6 × 1.0 × 10−4 × 1.60 × 10−19) = 1.3 × 1029 m−3. Converting mm2 with 10−3 gives 1.3 × 1026.

7. Which component obeys Ohm's law?

  1. A
    a filament lamp as its brightness increases
  2. B
    a semiconductor diode in forward bias
  3. C
    an NTC thermistor heated by the current in it
  4. D
    a metal wire kept at constant temperature in a water bath
Show answer

Answer: D. Ohm's law (I ∝ V) applies to a metallic conductor whose temperature and other physical conditions stay constant. In each of the other cases the resistance changes as the current changes.

8. A light-dependent resistor (LDR) is connected in series with an ammeter and a cell of negligible internal resistance. A bright lamp is moved closer to the LDR. What happens to the ammeter reading?

  1. A
    it increases
  2. B
    it decreases
  3. C
    it stays the same
  4. D
    it falls to zero
Show answer

Answer: A. More light falls on the LDR, so its resistance decreases. With the same e.m.f. and less resistance, the current increases.

9. A component has an I–V graph (current on the vertical axis) that curves upwards. At a p.d. of 2.0 V the current is 0.50 A, and the gradient of the tangent to the curve at this point is 0.40 A V−1. What is the resistance of the component at 2.0 V?

  1. A
    0.25 Ω
  2. B
    2.5 Ω
  3. C
    4.0 Ω
  4. D
    5.0 Ω
Show answer

Answer: C. Resistance is V/I at that point: 2.0 ÷ 0.50 = 4.0 Ω. The reciprocal of the tangent gradient (2.5 Ω) is not the resistance for a non-linear component.

10. When the p.d. across a resistor of constant resistance is increased from 3.0 V to 4.5 V, the current in it increases by 0.25 A. What is its resistance?

  1. A
    0.17 Ω
  2. B
    6.0 Ω
  3. C
    12 Ω
  4. D
    18 Ω
Show answer

Answer: B. For a constant resistance, R = ΔV/ΔI = 1.5 ÷ 0.25 = 6.0 Ω (so the currents are 0.50 A and 0.75 A). Dividing 4.5 V by the change in current gives 18 Ω.

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How many Electricity MCQs are there?

74, each with the answer and a short explanation, across 3 topics: Electric current, Potential difference and power, Resistance and resistivity. Every chapter test draws ten of them, so you can take it many times.

Is the AS Level Physics chapter 9 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

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