Lesson 4.1.2

4.1.2 Mean drift velocity Quiz: OCR Physics, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 4.1.2, Mean drift velocity: 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 is the typical magnitude of the mean drift velocity of charge carriers in metals?

    • Fraction of mm s⁻¹
    • Zero
    • Speed of light
    • Hundreds of m s⁻¹

  2. The current in a conductor is related to drift velocity by:

    • I = n A e v
    • I = n A e / v
    • I = n e v
    • I = n A v

  3. In the drift velocity equation I = nAev, what does the symbol n represent?

    • Drift speed
    • Total charge
    • Cross-sectional area
    • Number density

  4. How does the charge carrier density, n, of an insulator compare to a conductor?

    • Exactly equal
    • Nearly identical
    • Very much smaller
    • Very much larger

  5. What happens to the number density of charge carriers in a semiconductor as temperature increases?

    • It drops to zero
    • It increases
    • It stays constant
    • It decreases

  6. Typical free electron number density in a metal is about:

    • 10^28 per cubic metre
    • 10^10 per cubic metre
    • 10^3 per cubic metre
    • 10^19 per cubic metre

  7. Why is the mean drift velocity of electrons in a typical metal wire so small?

    • Very small voltage
    • High carrier density
    • Low carrier density
    • Zero current flow

  8. If the cross-sectional area of a wire carrying constant current is doubled, what happens to drift velocity?

    • It quadruples
    • It halves
    • It doubles
    • It stays constant

  9. A 2.0 A current flows through a wire of area 1.0 x 10^-6 m^2 with n = 8.5 x 10^28 m^-3. What is the drift velocity?

    • 1.5 x 10^-4 m s^-1
    • 1.5 x 10^-2 m s^-1
    • 2.9 x 10^-3 m s^-1
    • 6.8 x 10^-5 m s^-1

  10. A wire with n = 2.0 x 10^28 m^-3 and area 2.0 x 10^-6 m^2 has drift velocity 1.0 x 10^-4 m s^-1. What current flows?

    • 6.4 A
    • 64 A
    • 0.064 A
    • 0.64 A

  11. The cross-sectional area of a wire doubles while the drift velocity halves, with the same carrier density. The current:

    • Quadruples
    • Halves
    • Stays the same
    • Doubles

  12. For the same current, if the carrier density in a wire doubles, the drift velocity:

    • Quadruples
    • Doubles
    • Halves
    • Stays the same

  13. For the same current and area, the drift velocity in silicon compared with copper is about:

    • 10^12 times smaller
    • The same
    • 10^6 times smaller
    • 10^12 times larger

  14. A current of 1.2 A flows in a wire of cross-section 1.0 x 10^-6 m^2 with n = 6.0 x 10^28 m^-3. What is the drift velocity?

    • 1.3 x 10^-2 m s^-1
    • 2.0 x 10^-3 m s^-1
    • 7.8 x 10^-5 m s^-1
    • 1.3 x 10^-4 m s^-1

  15. At a drift velocity of 1.0 x 10^-4 m s^-1, how long would it take a carrier to move 1 m?

    • About 1 x 10^-4 s
    • About 1 x 10^6 s
    • About 1 x 10^4 s
    • About 1 x 10^2 s

  16. What is the direction of electron drift velocity relative to conventional current direction?

    • Same direction
    • Perpendicular direction
    • Random direction
    • Opposite direction

  17. Two wires of the same metal carry the same current. Wire B has half the cross-sectional area of wire A. The drift velocity in B compared with A is:

    • Quadrupled
    • The same
    • Halved
    • Doubled

  18. Why does current begin flowing almost instantaneously throughout a circuit when turned on?

    • Zero electron mass
    • Infinite carrier density
    • Electric field propagation
    • Fast electron drift

  19. A wire carries 5 A with n = 8.5 x 10^28 m^-3 and area 2 x 10^-6 m^2. What is the drift velocity?

    • 7.4 x 10^-5 m s^-1
    • 1.8 x 10^-4 m s^-1
    • 1.8 x 10^-2 m s^-1
    • 3.7 x 10^-4 m s^-1

  20. What provides the high number density of charge carriers in metallic conductors?

    • Positive ions
    • Delocalised electrons
    • Atomic nuclei
    • Bound protons

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