Edexcel GCSE Combined Science CP10 Electricity and circuits: a complete overview of current, voltage, resistance, circuits and power

What CP10 actually demands

Electricity and circuits, on Physics Paper 2, is calculation-heavy and rewards confident use of $V = IR$ and the power equations, a clear understanding of the series and parallel rules, and the ability to interpret current-voltage graphs.

This guide walks through the two halves of the topic and ties together the matching dot-point pages, each with its own practice questions.

Current, voltage and resistance

Current (amperes) is the rate of flow of charge; potential difference (volts) is the energy per unit charge; resistance (ohms) opposes the current. They are linked by:

Ohm's law: at constant temperature, current is proportional to voltage (a straight-line graph). A filament lamp's resistance rises as it heats (a curved graph); a diode only conducts one way.

Circuits, power and energy

In a series circuit, current is the same everywhere and voltage is shared; in a parallel circuit, each branch has the full voltage and current is shared. Electrical power and energy are:

The UK mains is alternating current at about 230 V and 50 Hz.

How CP10 is examined

• Calculations. Using $V = IR$, $P = IV$ and $E = Pt$.
• Graphs. Interpreting current-voltage characteristics for resistors, lamps and diodes.
• Circuit rules. Applying the series and parallel rules for current and voltage.
• Mains. Knowing the UK mains is a.c. at 230 V and 50 Hz.

Check your knowledge

A mix of recall and calculation questions covering CP10. Attempt them under timed conditions, then check against the solutions.

1. State the equation linking potential difference, current and resistance. (1 mark)
2. A 9 V supply drives a current through a 3 ohm resistor. Calculate the current. (2 marks)
3. State Ohm's law. (1 mark)
4. Why does a filament lamp not obey Ohm's law? (1 mark)
5. In a series circuit, what is shared between the components? (1 mark)
6. In a parallel circuit, what is the same across each branch? (1 mark)
7. Write the equation for electrical power in terms of current and voltage. (1 mark)
8. State the voltage and frequency of the UK mains supply. (2 marks)