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Electricity and Circuits

The atom, and drawing circuit diagrams

  • 3 things to know
  • Paper 2

Overview

The charges, relative masses and positions of protons, neutrons and electrons, why atoms are neutral, conventional current, and circuit symbols for cells, batteries, diodes, LEDs, variable resistors, lamps, light-dependent resistors, thermistors, motors, meters and switches.

What you need to know

Answer each one before you reveal it.

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Key term

State the charge of each of the two types of particle found in the nucleus of an atom.

Key term

What are the relative charges of a proton, a neutron and an electron?

Numbers

What are the relative masses of a proton, a neutron and an electron?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    State the charge of each of the two types of particle found in the nucleus of an atom.

    Model answer

    Protons carry a positive charge and neutrons carry no charge.

  2. 2

    What are the relative charges of a proton, a neutron and an electron?

    Model answer

    A proton has a relative charge of +1, a neutron has no charge, and an electron has a relative charge of −1.

  3. 3

    What are the relative masses of a proton, a neutron and an electron?

    Model answer

    A proton and a neutron each have a relative mass of 1, while an electron has a relative mass of about 1/1836, which is very nearly zero.

  4. 4

    Where in an atom are the electrons found?

    Model answer

    The electrons occupy shells at different distances around the outside of the nucleus.

  5. 5

    Why does a complete atom have no overall charge?

    Model answer

    An atom contains equal numbers of protons and electrons, so the positive and negative charges cancel out.

  6. 6

    Why is almost all the mass of an atom concentrated in a tiny part of its volume?

    Model answer

    The protons and neutrons carry nearly all the mass and are packed into the nucleus, which is far smaller than the whole atom.

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