BRAINCAKEBack e.m.f.
When a current-carrying coil is placed 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
- Motor effect
- The force experienced by a current-carrying conductor placed in an external magnetic field, resulting from the interaction between the field and the field created by the current.
- Magnetic flux
- The product of the magnetic flux density and the area through which the field passes at right angles to it, measured in weber.
- Magnetic flux linkage
- The product of the magnetic flux through a coil and the number of turns on the coil.
- Lenz's law
- The direction of an induced current is always such as to oppose the change that produced it.
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 AQA A-level Physics topics