Key learning points

1. Electric charge, Q, is measured in coulombs (C).
2. Electric current is a measure of the rate of flow of electric charge, calculated using: I = Q ÷ t.
3. Potential difference is a measure of the energy transferred by each coulomb of charge, calculated using: V = E ÷ Q.
4. Combining I = Q ÷ t and V = E ÷ Q gives the equation: E ÷ t = I × V. This is equivalent to P = I × V.
5. Unknown variables in the power equation can often be calculated using: I = V ÷ R.

Keywords

• Electric charge - an electrical property; it can either be positive or negative

• Coulombs (C) - the unit of electric charge

• Electric current - the amount of electric charge flowing past a point in a circuit each second

• Potential difference (p.d.) - the amount of energy transferred by each coulomb of charge, passing between two points in a circuit

• Power - the amount of energy transferred each second

Common misconception