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Electric charge & fields
Two simple rules: like charges push apart, opposites pull together. The space around them gets a 'pull arrow' at every point — that's the field.
Two-charge field
Drag the charges. Flip their signs.
Charge 1
Charge 2
Like signs repel. Opposites attract. Field strength falls as 1/r².
Two flavours of charge
Charge comes in two kinds — positive and negative. Atoms have positive protons in the nucleus and negative electrons around them. Rub two things together and you can steal electrons from one to the other — that's static electricity.
Coulomb's law
The force between two charges is
F = k · q₁ · q₂ / r². Strong when close, weak when far. Same shape as gravity — but the numbers say charges push or pull a trillion-trillion times harder.The field idea
Instead of asking "what force does charge A feel from charge B?", we say charge B fills the space with a field. Any charge that wanders into that space feels a push along the arrow at its location.
Field lines
- Arrows point away from positive charges, into negative ones.
- Where the arrows are dense, the field is strong.
- Lines never cross — the force has one direction at every point.