BRAINCAKEBack e.m.f.
When a current-carrying coil is place in a magnetic field it rotates due to the motor effect and the area swept out by the coil changes. This means that the magnetic flux linkage changes and an e.m.f. is induced in the coil. According to Lenz's law the induced e.m.f. acts in the opposite direction to the change that caused it. This means it acts to oppose the potential difference across the coil and is called the back e.m.f.
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Key terms in this lesson
- magnetic field
- A region of space in which a moving charge, current-carrying conductor or magnetic material experiences a force.
- motor effect
- The force produced on a current-carrying conductor placed in an external magnetic field.
- Lenz's law
- The direction of an induced current is always such as to oppose the change that caused it.
- magnetic flux
- The product of the magnetic flux density and the area through which the field lines pass at right angles.
- magnetic flux linkage
- The product of the magnetic flux through a coil and the number of turns on the coil.
More in Electromagnetic Induction
- Solenoid
- Lenz's Law
- Faraday's Law of Electromagnetic Induction
- The Alternating Current Generator
- Power Station Alternators
- Transformers
- Transformer Efficiency
- The National Grid
All 12 lessons in Electromagnetic Induction · All OCR A-level Physics topics