# Parallel Circuit

## Key Stage 3

### Meaning

A Parallel Circuit is an electrical circuit with two or more paths the current can flow along.

In a parallel circuit the current is split at junctions before taking a different path.
Switches can be placed in a Parallel Circuit to allow current along one path at a time.
Components placed in parallel with each other have the same Potential Difference across them.
 The current from the battery splits at the junction sharing the current between the two bulbs. The two bulbs in this parallel circuit can be switched on and off separately.

### Examples

 The cell, bulb and voltmeter are in parallel so they have the same potential difference across them. The two bulbs are in parallel so they have the same potential difference across them but may have a different current passing through them. The bulb and motor are in parallel so they have the same potential difference across them but may have a different current passing through them.

## Key Stage 4

### Meaning

A Parallel Circuit is an electrical circuit with two or more paths the current can flow along.

In a parallel circuit the current is split at junctions before taking a different path.
Switches can be placed in a parallel circuit to allow current along one path at a time.
Components placed in parallel with each other have the same potential difference across them.
 The current from the battery splits at the junction sharing the current between the two bulbs. The two bulbs in this parallel circuit can be switched on and off separately.

### Examples

 The cell, bulb and voltmeter are in parallel so they have the same potential difference across them. The two bulbs are in parallel so they have the same potential difference across them but may have a different current passing through them. The bulb and motor are in parallel so they have the same potential difference across them but may have a different current passing through them.

### 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.

### References

#### AQA

Parallel circuit, pages 54-5, 62-3, GCSE Physics; Student Book, Collins, AQA
Parallel circuits, page 29, GCSE Physics; The Revision Guide, CGP, AQA
Parallel circuits, page 302, GCSE Combined Science Trilogy 1, Hodder, AQA
Parallel circuits, pages 186, 187, GCSE Combined Science; The Revision Guide, CGP, AQA
Parallel circuits, pages 29, 30, GCSE Physics; The Revision Guide, CGP, AQA
Parallel circuits, pages 37, 47, GCSE Physics, Hodder, AQA
Parallel circuits, pages 60-61, GCSE Physics; Third Edition, Oxford University Press, AQA
Parallel circuits, pages 72-76, 78, 79, GCSE Combined Science Trilogy; Physics, CGP, AQA
Parallel circuits, pages 74-78, 80, 81, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA

#### Edexcel

Parallel circuits, page 141, GCSE Physics, Pearson Edexcel
Parallel circuits, page 75, GCSE Physics; The Revision Guide, CGP, Edexcel
Parallel circuits, pages 188, 189, GCSE Combined Science; The Revision Guide, CGP, Edexcel
Parallel circuits, pages 235-238, 240, GCSE Physics, CGP, Edexcel
Parallel circuits; resistors, page 147, GCSE Physics, Pearson Edexcel

#### OCR

Parallel circuits, page 181, Gateway GCSE Combined Science; The Revision Guide, CGP, OCR
Parallel circuits, pages 103, 111, 260-263, Gateway GCSE Physics, Oxford, OCR
Parallel circuits, pages 48, 49, Gateway GCSE Physics; The Revision Guide, CGP, OCR