Charge (Oxford AQA IGCSE Physics)

Revision Note

Charge

  • Charge is a property of matter

    • Charge is measured in units called coulombs, C

  • Objects can be positively charged, negatively charged or neutral (i.e. not charged)

    • Objects are neutral if the positive charge and negative charge cancel each other out

    • For example, a neutral atom has an equal number of protons (positively charged particles) and electrons (negatively charged particles

  • If a neutral object gains electrons, it becomes negatively charged

  • If a neutral object loses electrons, it becomes positively charged

  • When two charged objects are brought close together, there will be a force of attraction or repulsion between those objects

Positive and negative charges

Two positive charges repel each other. A positive charge is attracted towards a negative charge, for IGCSE & GCSE Physics revision notes
Like charges repel; opposite charges attract
  • Remember:

    • Opposite charges attract

    • Like charges repel

  • In some objects, the electrical charges can move easily around the object

    • For example, in metals such as copper, electrons can move easily around the metal

Potential difference

  • For an electrical charge to flow through a closed circuit, it must include a source of potential difference (p.d.)

    • This is often called voltage or e.m.f.

  • Sources of potential difference include:

    • A cell

    • Batteries (multiple cells)

    • Electrical generator

  • The terminals in a cell make one end of the circuit positive and the other negative

  • This sets up a potential difference across the circuit

    • The symbol for the potential difference is V

  • In a closed circuit with a source of potential difference, electrons flow through the metal wire from the negative end to the positive end

The flow of electrons

Electrons free from their metal ions move from the negative side of a wire to the positive side
In metals, the current is caused by a flow of electrons
  • The potential difference across a component in a circuit is defined as

The energy transferred per unit charge flowing from one point to another

Last updated:

You've read 0 of your 5 free revision notes this week

Sign up now. It’s free!

Join the 100,000+ Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Ann Howell

Author: Ann Howell

Expertise: Physics Content Creator

Ann obtained her Maths and Physics degree from the University of Bath before completing her PGCE in Science and Maths teaching. She spent ten years teaching Maths and Physics to wonderful students from all around the world whilst living in China, Ethiopia and Nepal. Now based in beautiful Devon she is thrilled to be creating awesome Physics resources to make Physics more accessible and understandable for all students, no matter their schooling or background.

Caroline Carroll

Author: Caroline Carroll

Expertise: Physics Subject Lead

Caroline graduated from the University of Nottingham with a degree in Chemistry and Molecular Physics. She spent several years working as an Industrial Chemist in the automotive industry before retraining to teach. Caroline has over 12 years of experience teaching GCSE and A-level chemistry and physics. She is passionate about creating high-quality resources to help students achieve their full potential.