Lesson 4.3.2

4.3.2 Internal resistance Quiz: OCR Physics, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 4.3.2, Internal resistance: 20 multiple choice questions for the OCR Physics (H156), Unit 3: Electrons, waves and photons, written with Revision Ninja.

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The 20 questions

  1. What term describes the resistance within a power source that causes lost volts?

    • Electromotive force
    • Internal resistance
    • Terminal p.d.
    • External resistance

  2. For a source of e.m.f. E and internal resistance r carrying current I, the terminal p.d. V is:

    • E - Ir
    • I/r
    • E + Ir
    • E/r

  3. The quantity lost volts for a cell is equal to:

    • Ir
    • E/I
    • r/I
    • E - r

  4. As the current drawn from a cell increases, what happens to its terminal p.d.?

    • It increases
    • It doubles
    • It stays constant
    • It decreases

  5. When zero current is drawn from a cell, its terminal potential difference equals its what?

    • Electromotive force
    • Internal resistance
    • Lost volts
    • Short-circuit current

  6. A cell of e.m.f. 1.5 V and internal resistance 0.20 ohm delivers a current of 2.0 A. What is its terminal p.d.?

    • 1.3 V
    • 1.1 V
    • 1.5 V
    • 0.4 V

  7. A 12 V cell with internal resistance 0.5 ohm is short-circuited. What is the short-circuit current?

    • 0.04 A
    • 6.0 A
    • 12.5 A
    • 24 A

  8. A cell of e.m.f. 6.0 V has terminal p.d. 5.4 V when delivering 2.0 A. What is its internal resistance?

    • 3.0 ohm
    • 0.6 ohm
    • 0.03 ohm
    • 0.3 ohm

  9. A cell has e.m.f. 2.0 V and internal resistance 1.0 ohm, connected to an external resistor of 3.0 ohm. What is the current?

    • 2.0 A
    • 0.67 A
    • 0.50 A
    • 0.33 A

  10. In the circuit of a 2.0 V cell with internal resistance 1.0 ohm and a 3.0 ohm external resistor, what is the terminal p.d.?

    • 2.0 V
    • 1.0 V
    • 1.5 V
    • 0.5 V

  11. On a graph of terminal p.d. V against current I for a cell, the y-intercept represents:

    • the power output
    • the internal resistance
    • the short-circuit current
    • the e.m.f.

  12. On a graph of terminal p.d. against current for a cell, the magnitude of the gradient represents:

    • the short-circuit current
    • the external resistance
    • the e.m.f.
    • the internal resistance

  13. A cell's V-I graph has V = 1.50 V at I = 0 and V = 1.20 V at I = 1.5 A. What is its internal resistance?

    • 0.20 ohm
    • 0.30 ohm
    • 0.80 ohm
    • 1.25 ohm

  14. In an experiment measuring internal resistance, what primary quantity does the variable resistor vary?

    • Internal resistance
    • Circuit current
    • Supply frequency
    • Cell e.m.f.

  15. For maximum power output from a source, load resistance must equal what quantity?

    • Internal resistance
    • Zero resistance
    • Double internal resistance
    • Infinite resistance

  16. Two identical cells, each of e.m.f. E and internal resistance r, are connected in parallel. What are the effective e.m.f. and internal resistance?

    • 2E and r
    • E and 2r
    • 2E and r/2
    • E and r/2

  17. Two identical cells, each of e.m.f. E and internal resistance r, are connected in series. What are the effective e.m.f. and internal resistance?

    • E and r/2
    • E and 2r
    • 2E and r
    • 2E and 2r

  18. A cell with e.m.f. 1.5 V and internal resistance 0.5 ohm drives an external resistor of 2.5 ohm. What power is dissipated in the external resistor?

    • 0.30 W
    • 1.5 W
    • 0.63 W
    • 0.75 W

  19. A cell's terminal p.d. is 4.0 V at 2.0 A and 5.0 V at 1.0 A. What are its e.m.f. and internal resistance?

    • E = 6.0 V, r = 2.0 ohm
    • E = 6.0 V, r = 1.0 ohm
    • E = 4.0 V, r = 0.5 ohm
    • E = 5.0 V, r = 1.0 ohm

  20. A cell with e.m.f. 1.5 V and internal resistance 0.10 ohm supplies a current of 3.0 A. What power is wasted inside the cell?

    • 0.30 W
    • 0.90 W
    • 4.5 W
    • 0.15 W

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