Contents
Key Stage 3
Meaning
A picture of a resistor.
A resistor is a component in an electrical circuit which makes it difficult to electricity to pass through it.
About Resistors
- A resistor is a component designed to have a particular resistance.
- Resistors are added to circuits to control the current which will pass through for a certain potential difference.
- The greater the resistance of a resistor the smaller the current will be.
- The resistance of a resistor can be found by attaching an ammeter in series with the resistor and a voltmeter in parallel with the resistor.
- All components in a circuit act as resistors, including wires. The longer a wire the more resistance it will have to a current.
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| A resistor. | The symbol for a resistor. |
Key Stage 4
Meaning
The symbol for a resistor.
A resistor is a component in an electrical circuit which makes it difficult to electricity to pass through it.
About Resistors
- A resistor is a component designed to have a particular resistance.
- Resistors are added to circuits to control the current which will pass through for a certain potential difference.
- The greater the resistance of a resistor the smaller the current will be.
- The resistance of a resistor can be found by attaching an ammeter in series with the resistor and a voltmeter in parallel with the resistor.
- All components in a circuit act as resistors, including wires. The longer a wire the more resistance it will have to a current.
Resistors in Series
- Adding resistors in series increases the resistance in the circuit.
- The resistance of each resistor can be added together.
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The resistance between points A and B is:
5Ω. |
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The resistance between points A and B is:
2Ω + 5Ω = 7Ω |
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The resistance between points A and B is:
2Ω + 5Ω + 9Ω = 16Ω |
Resistors in Parallel
NB: You only need to know what happens with identical resistors in parallel.
- When identical resistors are added in parallel there are more paths for the electricity so the resistance is reduced.
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| Two identical resistors in Parallel circuit gives twice the number of paths, so has half the resistance.
The resistance between points A and B is 12Ω. |
Three identical resistors in Parallel circuit gives three times the number of paths, so has a third of the resistance.
The resistance between points A and B is 8Ω. |
Four identical resistors in Parallel circuit gives four times the number of paths, so has a quarter of the resistance.
The resistance between points A and B is 6Ω. |
IV Graph
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Description
- The IV Graph for a resistor shows that
- As potential difference increases, increases.
- The relationship between potential difference and current is linear (the gradient is constant).
- The current is directly proportional to potential difference.
Explanation
- Resistors obey Ohm's Law so the "current through a resistor at constant temperature is directly proportional to the potential difference across the resistor."