Lesson T5.3.3

T5.3.3 Electromagnets and D.C. motors Quiz: KS3 Physics, Unit 5

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson T5.3.3, Electromagnets and D.C. motors: 20 multiple choice questions for the KS3 Physics (National Curriculum), Unit 5: Electricity and magnetism, written with Revision Ninja.

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The 20 questions

  1. A current flowing through a wire produces:

    • A gravitational field around the wire
    • A magnetic field around the wire
    • Heat only, with no field
    • An electric field only inside the wire

  2. What is a solenoid?

    • A coil of wire carrying a current
    • A battery with a metal core
    • A permanent magnet made of plastic
    • A bar magnet with two poles

  3. What makes an electromagnet stronger?

    • Making the coil from fewer turns
    • Using a smaller current
    • Adding an iron core inside the coil
    • Using a plastic core inside the coil

  4. Which change makes an electromagnet stronger?

    • Decreasing the current through the coil
    • Removing the coil from the circuit
    • Reversing the battery, with no other change
    • Increasing the current through the coil

  5. An electromagnet is different from a permanent magnet because it:

    • Can be switched on and off
    • Has no north or south pole
    • Is always weaker than a permanent magnet
    • Cannot attract iron

  6. Which of these is a common use of an electromagnet?

    • A plastic ruler
    • A compass needle
    • An electric bell
    • A glass lens

  7. Which of these is a DC motor's main purpose?

    • To store electrical charge for later use in a circuit
    • To measure the temperature of a room accurately
    • To turn electrical energy into kinetic energy
    • To turn light energy into heat energy for warming

  8. Why does a current-carrying wire placed in a magnetic field experience a force?

    • The wire becomes much heavier whenever a current flows through it
    • The wire is attracted by the magnetic field of the Sun's surface
    • Current makes the wire expand sideways and push on its surroundings
    • The current's magnetic field interacts with the external magnetic field

  9. In a simple DC motor, what does the coil do when a current flows through it?

    • It heats up and stops
    • It emits light and then stops
    • It turns because of the force on the coil
    • It stays still because the magnet holds it

  10. What does the commutator do in a DC motor?

    • It stops the coil from rotating once it has started to turn
    • It stores electric charge in a small capacitor for later use
    • It reverses the current each half turn so the coil keeps turning
    • It heats the coil so that it expands and turns the motor faster

  11. Which change would reverse the direction a DC motor turns?

    • Making the permanent magnet weaker in strength
    • Adding a plastic casing around the motor body
    • Reversing the direction of the current
    • Increasing the size of the current flowing through

  12. A DC motor turns faster when which change is made?

    • The current is decreased
    • The current is increased
    • The magnet is removed
    • The coil is made from plastic

  13. What happens to the magnetic field of an electromagnet when the current is switched off?

    • The field stays permanently in the coil and iron
    • The field moves across to the iron core inside
    • The field disappears, or almost disappears
    • The field gets stronger as the coil cools down

  14. Why is a relay useful?

    • It reverses the direction of a current in the circuit
    • It uses a small current to switch on a larger, separate circuit
    • It converts sound waves into light energy for display
    • It stores energy in a battery for use in later circuits

  15. Which part of a simple DC motor is a coil of wire?

    • The switch
    • The commutator
    • The battery
    • The armature

  16. A solenoid has a magnetic field much like which object?

    • A bar magnet
    • A resistor
    • A lens
    • A battery

  17. Why does an electromagnet with more turns of wire become stronger?

    • More turns make the iron core much heavier and harder to move
    • More turns cancel out part of the field, so it becomes weaker
    • Each turn adds to the magnetic field, so the total field is bigger
    • More turns reduce the current that flows through the coil

  18. What is the main job of the magnet in a simple DC motor?

    • To store electric charge for the motor during its operation
    • To provide a magnetic field for the coil to push against
    • To cool the coil so that it does not overheat in use
    • To generate electricity for the battery as the coil spins round

  19. Which change would make a DC motor weaker?

    • Adding a stronger magnet
    • Using a larger current
    • Adding more turns to the coil
    • Using a smaller current

  20. Why does a current-carrying wire produce a magnetic field only while the current flows?

    • The field is stored in the wire's metal
    • Air carries the field away when the current stops
    • The magnetic field depends on the current that creates it
    • Wires are always neutral and never produce fields

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