Resistor
Contents
Key Stage 3
Meaning
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.
A resistor. | The symbol for a resistor. |
Key Stage 4
Meaning
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.
The resistance between points A and B is:
5Ω. | |
The resistance between points A and B is:
2Ω + 5Ω = 7Ω | |
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.
Two identical resistors in parallel 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 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 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
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."
Obtaining the IV Graph
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References
AQA
- Resistor, pages 46-7, 52, GCSE Physics; Student Book, Collins, AQA
- Resistor; non-ohmic, page 59, GCSE Physics; Student Book, Collins, AQA
- Resistors in parallel, pages 55, 63, GCSE Physics; Student Book, Collins, AQA
- Resistors in series, pages 54, 57, 63, GCSE Physics; Student Book, Collins, AQA
- Resistors, pages 293, 295-6, GCSE Combined Science Trilogy 1, Hodder, AQA
- Resistors, pages 40-1, GCSE Physics, Hodder, AQA
- Resistors, pages 52-53, 55, 58-59, 61, 70, GCSE Physics; Third Edition, Oxford University Press, AQA
- Resistors, pages 60, 66, 77-79, GCSE Combined Science Trilogy; Physics, CGP, AQA
- Resistors, pages 62, 68, 79-81, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
- Resistors; circuit symbol, page 38, GCSE Physics, Hodder, AQA
- Resistors; I-V characteristics, pages 65, 66, GCSE Combined Science Trilogy; Physics, CGP, AQA
- Resistors; I-V characteristics, pages 67, 68, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
- Resistors; light-dependant resistors (LDRs), pages 60, 80, 81, GCSE Combined Science Trilogy; Physics, CGP, AQA
- Resistors; light-dependant resistors (LDRs), pages 62, 82, 83, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
- Resistors; light-dependent (LDRs), pages 299-300, GCSE Combined Science Trilogy 1, Hodder, AQA
- Resistors; ohmic and non-ohmic, page 298, GCSE Combined Science Trilogy 1, Hodder, AQA
- Resistors; ohmic and non-ohmic, page 43, GCSE Physics, Hodder, AQA
- Resistors; thermistors, pages 298-9, GCSE Combined Science Trilogy 1, Hodder, AQA
- Resistors; thermistors, pages 60, 80, 81, GCSE Combined Science Trilogy; Physics, CGP, AQA
- Resistors; thermistors, pages 62, 82, 83, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
- Resistors; variable resistors, pages 60, 65, GCSE Combined Science Trilogy; Physics, CGP, AQA
- Resistors; variable resistors, pages 62, 67, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA
Edexcel
- Resistors (fixed), page 228, GCSE Physics, CGP, Edexcel
- Resistors; parallel circuits, page 147, GCSE Physics, Pearson Edexcel
- Resistors; series circuits, pages 146-147, GCSE Physics, Pearson Edexcel