Lesson 3.1.2

3.1.2 Resistance, Ohm's law and I-V characteristics Quiz: Pearson Edexcel Physics, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.1.2, Resistance, Ohm's law and I-V characteristics: 20 multiple choice questions for the Pearson Edexcel Physics (9PH0), Unit 3: Electric Circuits, written with Revision Ninja.

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The 20 questions

  1. Resistance is defined by the equation:

    • R = V^2/I
    • R = I/V
    • R = V/I
    • R = VI

  2. Ohm's law states that, for a conductor at constant temperature:

    • The current is independent of the potential difference.
    • The current is directly proportional to the potential difference.
    • The resistance is directly proportional to the current.
    • The potential difference is inversely proportional to the current.

  3. The current-potential difference graph of an ohmic conductor at constant temperature is:

    • A straight line through the origin
    • A horizontal straight line
    • A curve through the origin
    • A straight line that does not pass through the origin

  4. For a filament lamp, the current-potential difference graph is:

    • A curve, with resistance increasing as the temperature rises
    • A horizontal line showing constant current
    • A curve, with resistance decreasing as the temperature rises
    • A straight line, because the lamp is ohmic

  5. The resistance of a negative temperature coefficient (NTC) thermistor as its temperature rises is:

    • Decreasing
    • Increasing
    • Constant
    • Infinite

  6. A diode conducts easily in one direction. In reverse bias, its resistance is:

    • Equal to the supply emf
    • Constant and equal to its forward resistance
    • Very high
    • Zero

  7. A resistor of 4.0 ohm carries a current of 2.0 A. What is the potential difference across it?

    • 2.0 V
    • 8.0 V
    • 6.0 V
    • 0.5 V

  8. A component has a potential difference of 12 V and a current of 0.30 A. What is its resistance?

    • 4.0 ohm
    • 0.025 ohm
    • 40 ohm
    • 3.6 ohm

  9. On the I-V graph of a component, the current is 0.20 A at 6.0 V. What is the resistance at this point?

    • 1.2 ohm
    • 0.033 ohm
    • 6.2 ohm
    • 30 ohm

  10. A filament lamp has a current of 1.5 A at 6.0 V and a current of 2.0 A at 12 V. Which statement is correct?

    • The resistance is constant at 4.0 ohm, so the lamp is ohmic.
    • The resistance increases from 4.0 ohm to 6.0 ohm, so the lamp is not ohmic.
    • The resistance decreases from 6.0 ohm to 4.0 ohm, so the lamp is not ohmic.
    • The resistance decreases from 4.0 ohm to 6.0 ohm, so the lamp is ohmic.

  11. Why does the resistance of a metal wire increase as its temperature rises?

    • Lattice ions vibrate more, causing more collisions that impede the conduction electrons.
    • Its number of charge carriers doubles.
    • Its lattice shrinks and holds electrons more tightly.
    • Its conduction electrons are removed by heat.

  12. Why does the resistance of a thermistor fall as its temperature rises?

    • More conduction electrons are released from the lattice, increasing the number of charge carriers.
    • Its lattice vibrations become less frequent.
    • Its conduction electrons slow down.
    • It becomes a superconductor.

  13. A resistor has a resistance of 10 ohm. The potential difference across it doubles from 5 V to 10 V. What happens to the current?

    • It halves from 0.5 A to 0.25 A.
    • It doubles from 0.5 A to 1.0 A.
    • It increases to 2.0 A.
    • It stays at 0.5 A.

  14. A student tests Ohm's law. Why must the temperature of the conductor be kept constant?

    • Temperature changes the current directly, without changing the resistance.
    • Temperature only affects the voltmeter reading.
    • Its resistance changes with temperature, so the I-V relationship would not be linear otherwise.
    • Constant temperature makes the conductor a superconductor.

  15. A resistor is connected to a 9.0 V supply and carries a current of 3.0 A. What is the power dissipated in the resistor?

    • 27 W
    • 6.0 W
    • 12 W
    • 3.0 W

  16. A diode is connected in forward bias with a potential difference of 0.7 V and a current of 0.02 A. What is its resistance?

    • 0.72 ohm
    • 35 ohm
    • 0.014 ohm
    • 350 ohm

  17. A component's I-V graph gets steeper as the potential difference increases. What does this indicate about its resistance?

    • The resistance increases as the potential difference increases.
    • The resistance is zero.
    • The resistance is constant.
    • The resistance decreases as the potential difference increases.

  18. A 2.5 ohm resistor and a 7.5 ohm resistor are each connected alone across the same 5.0 V supply. What is the ratio of the current in the 2.5 ohm resistor to that in the 7.5 ohm resistor?

    • 1 : 3
    • 1 : 2
    • 2 : 1
    • 3 : 1

  19. A resistor of resistance 50 ohm has a potential difference of 2.0 V across it. What current flows?

    • 25 A
    • 0.025 A
    • 0.040 A
    • 100 A

  20. Which component has a resistance that decreases as the light falling on it increases?

    • Light-dependent resistor (LDR)
    • Ohmic resistor
    • Filament lamp
    • Metal wire at constant temperature

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