What Is Electric Charge?
Everything around you — your desk, the air, your own body — is made of atoms. At the centre of each atom is a nucleus containing protons and neutrons, surrounded by a cloud of electrons. The key to electricity lies in two of these particles.
A fundamental property of matter that causes it to experience a force when placed in an electric field. Charge can be positive (+) or negative (−).
Here are the charge rules you need to know:
- Protons carry a positive charge (+)
- Electrons carry a negative charge (−)
- Neutrons carry no charge (they are neutral)
Normally, atoms have equal numbers of protons and electrons, so their charges cancel out — the atom is electrically neutral. When electrons are transferred from one object to another, one object gains extra electrons (becomes negatively charged) and the other loses electrons (becomes positively charged).
It is always electrons that are transferred when objects become charged — protons are locked tightly in the nucleus and do not move in everyday situations.
The Law of Electric Charges
Once objects carry charge, they exert forces on each other. This behaviour follows a simple but powerful rule:
Like charges repel each other; unlike (opposite) charges attract each other.
This can be summarised as:
| Charges | Interaction |
|---|---|
| + and + | Repel (push apart) |
| − and − | Repel (push apart) |
| + and − | Attract (pull together) |
Think of electric charges like magnets. Two north poles push away from each other, two south poles push away, but a north and south pole snap together. Charges behave the same way — opposites attract!
These forces act at a distance — the two charged objects do not need to touch each other for the force to be felt. This is called an action at a distance force, and it is explained by the concept of an electric field.
12 more sections in this topic
Pick this up in your Library: it holds the whole topic, notes, cheatsheet and questions.