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Electricity and Circuits

The heating effect of an electric current

  • 2 things to know
  • Paper 6

Overview

Why a resistor warms when current passes, heating elements, energy dissipated as thermal energy, electrons colliding with lattice ions, and why thick, short, copper cables waste less.

What you need to know

Answer each one before you reveal it.

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Key term

What happens to a resistor when there is a current in it?

Key term

Which energy store increases when a current passes through a resistance wire?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What happens to a resistor when there is a current in it?

    Model answer

    Energy is transferred to the resistor and it becomes hotter.

  2. 2

    Which energy store increases when a current passes through a resistance wire?

    Model answer

    The thermal energy store of the wire increases.

  3. 3

    Why does the flex of an electric heater feel warm after the heater has been running?

    Model answer

    There is a current in the resistance of the flex, so some energy is transferred to the thermal energy store of the wire.

  4. 4

    Which part of an electric toaster is designed to become hot when there is a current in it?

    Model answer

    The heating elements, which are wires of high resistance.

  5. 5

    What can be observed when a large current passes through a thin resistance wire?

    Model answer

    The wire heats up and may glow, showing that energy is being transferred to it.

  6. 6

    What happens to the energy transferred when a current does work against the resistance of a wire?

    Model answer

    It is dissipated as thermal energy, heating the wire and then the surroundings.

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