Electric Charge (AQA GCSE Physics): Revision Note

Electric Forces Between Charges

• The charge of a particle is either:

  • Positive

  • Negative

  • Neutral (no charge)

• Electrons are negatively charged particles, whilst protons are positive and neutrons are neutral

• This is why in a neutral atom, the number of electrons is equal to the number of protons

  • This is so the equal (but opposite) charges cancel out to make the overall charge of the atom zero

The number of negative electrons in an atom balances the number of positive protons

• Therefore, an object becomes negatively charged when it gains electrons and positively charged when it loses electrons

• When two charged particles or objects are close together, they also exert a force on each other

• This force could be:

  • Attractive (the objects get closer together)

  • Repulsive (the objects move further apart)

• Whether two objects attract or repel depends on their charge

  • If the charges are the opposite, they will attract

  • If the charges are the same, they will repel

• When a person touches a charged object, electrons move between them and the person ends up with the same type of charge as the object

  • For example, touching a negatively charged dome makes the person (and their hair) negatively charged

  • Each hair then has the same charge, so the hairs repel each other and stand on end

Opposite charges attract, like charges repel

Attraction or Repulsion Summary Table

• Attraction and repulsion between two charged objects are examples of a non-contact force

  • This is a force that acts on an object without being physically in contact with it