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Alternating Current

Key Stage 4

Meaning

An alternating current is an electrical current which changes direction.

About Alternating Currents

Alternating currents are caused by alternating potential differences.
Alternating currents have a frequency at which they alternate.
Mains electricity is an alternating current working at a frequency of 50Hz, so the current changes direction 50 times every second.
Alternating currents cannot be used to charge a cell or battery.
Alternating currents cannot be used in electrolysis.
Alternating currents are used in transformers.

Examples

OscilloscopeScreenAC1.png
An oscilloscope trace of mains electricity shows its frequency is 50Hz as the time period is 0.02s per oscillation and the peak potential difference is 320V, but the average over time is 230V.

References

AQA

Alternating current (a.c.), page 305, GCSE Combined Science Trilogy 1, Hodder, AQA'
Alternating current (a.c.), page 50, GCSE Physics, Hodder, AQA'
Alternating current (a.c.), pages 46, 66, GCSE Physics; Student Book, Collins, AQA'
Alternating current, pages 64-65, 224-229, GCSE Physics; Third Edition, Oxford University Press, AQA'
Alternating currents (a.c), page 188, GCSE Combined Science; The Revision Guide, CGP, AQA'
Alternating currents (ac), pages 31, 96, 97, GCSE Physics; The Revision Guide, CGP, AQA'
Alternating currents (ac), pages 86, 203, GCSE Combined Science Trilogy; Physics, CGP, AQA'
Alternating currents (ac), pages 89, 245, 306, GCSE Physics; The Complete 9-1 Course for AQA, CGP, AQA'

Edexcel

Alternating current (a.c.), pages 397, 411, GCSE Combined Science, Pearson Edexcel
Alternating current (a.c), pages 157, 174, GCSE Physics, Pearson Edexcel
Alternating currents, page 246, GCSE Physics, CGP, Edexcel
Alternating currents, pages 169, 192, 199, GCSE Combined Science; The Revision Guide, CGP, Edexcel
Alternating currents, pages 45, 79, 89, GCSE Physics; The Revision Guide, CGP, Edexcel

OCR

Alternating currents, page 214, Gateway GCSE Combined Science; The Revision Guide, CGP, OCR