Resistance changes in thermistors and LDRs

Resistance changes in thermistors and LDRs Quiz

Spec 79–80 · Edexcel International A Level Physics: Quiz

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  1. 1. What causes the resistance of a metal wire to rise when heated?

    • A. Lattice ions vibrate more, so collisions with electrons are more frequent
    • B. More conduction electrons are released
    • C. The electrons move more slowly between collisions only
    • D. The wire becomes thinner

  2. 2. An NTC thermistor is heated. Which describes what happens?

    • A. Number of conduction electrons decreases; resistance rises
    • B. Number of conduction electrons increases; resistance falls
    • C. Number of conduction electrons is constant; resistance rises
    • D. Number of conduction electrons increases; resistance rises

  3. 3. An LDR's resistance changes from 40 kΩ in the dark to 400 Ω in light. By what factor does it fall?

    • A. 10
    • B. 40
    • C. 100
    • D. 400

  4. 4. A thermistor of resistance 800 Ω is connected across a 4.0 V supply. What is the current?

    • A. 0.20 mA
    • B. 3.2 A
    • C. 5.0 mA
    • D. 200 mA

  5. 5. Why is an LDR's resistance lower in bright light than in the dark?

    • A. Light increases lattice vibrations
    • B. Light removes electrons from the circuit
    • C. Light increases the length of the LDR
    • D. Light releases electrons, so there are more conduction electrons

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