AQA GCSE Combined Science Physics - Electricity

What is current?

The flow of electric charge (electrons) around a circuit, measured in amperes (A).

What is potential difference (voltage)?

The energy transferred per unit of charge, measured in volts (V).

What is resistance?

A measure of how much a component resists the flow of current, measured in ohms (Ω).

What happens to current if resistance increases (with fixed voltage)?

The current decreases.

What is an ohmic conductor?

A component where current is directly proportional to voltage — resistance stays constant.

What does the current–voltage graph look like for an ohmic conductor?

A straight line through the origin.

How does a filament lamp behave?

As current increases, the lamp gets hotter and resistance increases — the graph curves.

What is a diode?

A component that only lets current flow in one direction.

What does an LDR (light dependent resistor) do?

Resistance decreases as light intensity increases.

What does a thermistor do?

Resistance decreases as temperature increases.

What is a series circuit?

A circuit where all components are in one loop — current is the same everywhere.

How is voltage shared in a series circuit?

It’s shared between all components.

What is a parallel circuit?

A circuit with branches — each component gets the full voltage.

How is current shared in a parallel circuit?

It splits between the branches depending on resistance.

What happens to total resistance in a parallel circuit when you add more resistors?

It decreases.

What is the UK mains electricity supply?

230 V, alternating current (AC), 50 Hz.

What is the difference between AC and DC?

AC = current changes direction, DC = current flows in one direction.

What is the function of the live wire?

Carries the alternating voltage from the power supply (brown wire).

What is the function of the neutral wire?

Completes the circuit — carries current away (blue wire).

What is the function of the earth wire?

Safety wire that prevents electric shock — only carries current if there’s a fault (green/yellow).

Why is the earth wire important?

It directs the current safely into the ground if the live wire touches the case.

What does a fuse do?

Breaks the circuit if too much current flows — protects the appliance.

What is power in an electrical appliance?

The rate at which it transfers energy.

Why do high-power devices use more energy?

They transfer more energy per second.

What is the national grid?

A network of cables and transformers that distributes electricity across the country.