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Charge and Current

Elementary charge, charge carriers and Kirchhoff's first law

  • 3 things to know
  • Papers 2 and 3

Overview

Recall questions on the elementary charge and quantisation of charge, charge carriers in metals and electrolytes, conventional current and electron flow, and Kirchhoff's first law as conservation of charge.

What you need to know

Answer each one before you reveal it.

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Key term

What is the value of the elementary charge e?

Key term

What charge does an electron carry?

Key term

What charge does a proton carry?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is the value of the elementary charge e?

    Model answer

    1.6 × 10⁻¹⁹ C

  2. 2

    What charge does an electron carry?

    Model answer

    An electron carries a charge of −e (negative elementary charge).

  3. 3

    What charge does a proton carry?

    Model answer

    A proton carries a charge of +e (positive elementary charge).

  4. 4

    What does it mean for electric charge to be quantised?

    Model answer

    Net charge on a particle or object can only exist as integer multiples of the elementary charge e.

  5. 5

    Why can an object never have a charge of 2.4 × 10⁻¹⁹ C?

    Model answer

    Because charge is quantised and can only exist as integer multiples of e (1.6 × 10⁻¹⁹ C), and 2.4 × 10⁻¹⁹ C is not an integer multiple of e.

  6. 6

    What causes electric current in metals?

    Model answer

    Electric current in metals is due to the movement of free electrons.

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