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Auralith Learning

Year 8 · Science · Electricity and magnetism · Lesson 2

Voltage (potential difference)

What voltage (potential difference) is, how to measure it with a voltmeter, and how it behaves in series and parallel circuits.

Whiteboard video lesson: Voltage (potential difference)

26-minute video lesson

Teaching, worked examples and 20 practice questions solved step by step.

Watch free for a month

What your child will learn

  • Describe voltage as the push that drives current
  • Connect a voltmeter correctly
  • Calculate voltages in series circuits
  • Describe voltage in parallel circuits
  • Add the voltages of cells in series

The method

  1. Voltage (potential difference) is the push that drives current, measured in volts (V).
  2. A voltmeter is connected across (in parallel with) a component.
  3. In series, the voltages across the components add up to the supply voltage.
  4. In parallel, each branch has the same voltage as the supply.

Key words: voltage, potential difference, volt, voltmeter, series, parallel, cell, battery.

Worked examples

The first three practice questions from the lesson, with every step.

Question 1

The battery is 9 V. The voltmeter V₁ reads 4 V. What does V₂ read?

  1. Step 1: Look at the circuit
  2. Step 2: Series: the voltages add up to the supply
  3. Step 3: V₂ = 9 − 4 = 5 V

Answer: 5 V

Question 2

The battery is 12 V. The voltmeter V₁ reads 7.5 V. What does V₂ read?

  1. Step 1: Look at the circuit
  2. Step 2: Series: the voltages add up to the supply
  3. Step 3: V₂ = 12 − 7.5 = 4.5 V

Answer: 4.5 V

Question 3

The battery is 4.5 V. The voltmeter V₂ reads 3 V. What does V₁ read?

  1. Step 1: Look at the circuit
  2. Step 2: Series: the voltages add up to the supply
  3. Step 3: V₁ = 4.5 − 3 = 1.5 V

Answer: 1.5 V