AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Current, resistance and potential difference: Questions will be set using the term potential difference. Students will gain credit for the correct use of either potential difference or voltage.
Potential difference is the energy transferred per unit charge between two points in a circuit, measured in volts (V).
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Potential difference is the energy transferred per unit charge between two points in a circuit, measured in volts (V). One volt equals one joule per coulomb, so a 6 V battery transfers 6 J of energy to each coulomb of charge passing through it. In exam questions, the term used will be potential difference, but answers that correctly use voltage are equally acceptable. When solving problems, identify the two points across which the energy transfer occurs, such as across a resistor or a lamp, then apply V = IR or energy transferred = charge × potential difference. Always give the unit V and show substitution clearly.
What earns the marks
- States that potential difference is the energy transferred per unit charge between two points in a circuit.
- Recalls that the unit of potential difference is the volt (V), where 1 V = 1 J/C.
- Uses either potential difference or voltage correctly in written answers and calculations.
- Applies V = IR or E = QV to find potential difference, current, resistance or energy transferred.
- Reads circuit diagrams to identify the two points across which the potential difference is measured.
Common mistakes and how to put them right
Writing that potential difference is the same as current.
Put it right by stating that current is the rate of flow of charge, while potential difference is energy transferred per unit charge.
Using the wrong unit, such as writing 6 A for a potential difference.
Put it right by checking that potential difference is always measured in volts (V).
Assuming voltage and potential difference are different quantities.
Put it right by treating them as two names for the same quantity, so either term earns credit.
Exam tips
- Use the term potential difference in your answer, but do not worry if you naturally write voltage, because both are accepted.
- Always include the unit V with a numerical answer and show the equation you used before substituting values.
- When a question gives energy and charge, divide energy by charge to find potential difference, and check the unit is V.
Try the lesson
The start of the Current, resistance and potential difference: Questions will be set using the term potential difference. Students will gain credit for the correct use of either potential difference or voltage. lesson, made from checked teaching notes for this specification point.
Have a go first
When discussing electrical circuits, which two terms are used interchangeably to describe the energy transferred per unit of charge?
Key words
Say what each word means before you turn the card.
potential difference
Try answering aloud or in your head before turning the card.
voltage
Try answering aloud or in your head before turning the card.
volt
Try answering aloud or in your head before turning the card.
current
Try answering aloud or in your head before turning the card.
See every definition
- potential difference
- The energy transferred per unit charge between two points in a circuit, measured in volts (V).
- voltage
- A name for the same quantity as potential difference, so either term earns credit in answers.
- volt
- The unit of potential difference, where one volt equals one joule per coulomb.
- current
- The rate of flow of charge, which is not the same as potential difference.
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Test your understanding of Current, resistance and potential difference: Questions will be set using the term potential difference. Students will gain credit for the correct use of either potential difference or voltage.
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