# Calculating with electric charge: including complex calculations

I can explain the equations: I = Q ÷ t, V = E ÷ Q, P = I × V, and V = I × R, and use them in calculations.

# Calculating with electric charge: including complex calculations

I can explain the equations: I = Q ÷ t, V = E ÷ Q, P = I × V, and V = I × R, and use them in calculations.

## Lesson details

### Key learning points

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

### Common misconception

Understanding electrical circuits is about memorising equations and procedures.

Give pupils the opportunity to discuss what happens in a circuit before they attempt to answer questions about it.

### Keywords

Electric current - 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

### Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

## Video

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## Starter quiz

### 6 Questions

current -

charge flowing past a point in a circuit per second

electric charge -

a property that can either be positive or negative

potential difference -

energy transferred per unit charge passing between two points

current -

A

energy -

J

potential difference -

V

power -

W

## Exit quiz

### 6 Questions

$$E$$ -

J

$$I$$ -

A

$$P$$ -

W

$$Q$$ -

C

$$t$$ -

s

$$V$$ -

V