AQA · GCSE · Physics
Course version: 8463 · Version from Sept 2016
The current (I) through a component depends on both the resistance (R) of…
Full specification wording
Current, resistance and potential difference: The current (I) through a component depends on both the resistance (R) of the component and the potential difference (V) across the component.
Two quantities decide the current in a component: the potential difference across it and its resistance.
Checked against the AQA 8463 specification (opens in a new tab) on .
- Point 1 of 4
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Two quantities decide the current in a component: the potential difference across it and its resistance. Potential difference is the push, so raising it drives a bigger current; resistance opposes the flow, so raising it cuts the current down. Both act together through V = I R, which rearranges to I = V ÷ R. That is why a circuit can be controlled in two separate ways. You can change the push, by adding or removing cells or by turning up a variable power supply, or you can change the opposition, by adjusting a variable resistor or adding further resistors. Both appear in practical questions asking how the potential difference across a component could be varied, and both are credited.
What earns the marks
- Identifying potential difference and resistance as the two quantities that set the current.
- A method of varying the potential difference, such as adjusting a variable resistor.
- An alternative method, such as changing the number of cells or the supply setting.
- Using I = V ÷ R correctly to support the reasoning.
Common mistakes and how to put them right
Naming only the battery as the thing that controls the current, ignoring resistance altogether.
Suggesting you change the component being investigated in order to vary the potential difference across it.
Writing use the variable resistor without saying it changes the resistance and so the pd.
Assuming current stays fixed when extra components are added to the circuit.
Exam tips
- Give one way of varying the pd precisely; adding another cell and adjusting a variable resistor are both accepted.
- Keep the direction of each effect straight: more pd gives more current, more resistance gives less.
- Quote I = V ÷ R when explaining a change so the examiner sees the reasoning, not just the conclusion.
Try the lesson
The start of the Current, resistance and potential difference: The current (I) through a component depends on both the resistance (R) of the component and the potential difference (V) across the component. lesson, made from checked teaching notes for this specification point.
Have a go first
A student wants to decrease the current flowing through a component in a circuit. Assuming the potential difference remains constant, what change should they make to the component?
Listen
Two quantities decide the current in a component: the potential difference across it and its resistance. Potential difference is the push, so raising it drives a bigger current; resistance opposes the flow, so raising it cuts the current down. Both act together through V = I R, which rearranges to I = V ÷ R. That is why a circuit can be controlled in two separate ways. You can change the push, by adding or removing cells or by turning up a variable power supply, or you can change the opposition, by adjusting a variable resistor or adding further resistors. Both appear in practical questions asking how the potential difference across a component could be varied, and both are credited. A strong answer earns marks for these points. identifying potential difference and resistance as the two quantities that set the current. a method of varying the potential difference, such as adjusting a variable resistor. an alternative method, such as changing the number of cells or the supply setting. using I = V ÷ R correctly to support the reasoning. Exam tip: Give one way of varying the pd precisely; adding another cell and adjusting a variable resistor are both accepted.
Key words
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potential difference
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resistance
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variable resistor
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controlling current
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See every definition
- potential difference
- The push across a component that drives a bigger current when it is raised.
- resistance
- The opposition to the flow of current, which cuts the current down when it is raised.
- variable resistor
- A component that can be adjusted to change the resistance and so the potential difference.
- controlling current
- Changing the push by adding or removing cells or turning up a variable power supply, or changing the opposition by adjusting a variable resistor or adding further resistors.
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