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Faraday laws; static vs dynamic emf

Short answer

Faraday's first law: emf is induced when flux linking a coil changes. Second law: magnitude = N dφ/dt, direction opposes the cause (Lenz's law, e = –N dφ/dt). Statically induced emf arises from time-varying flux without motion (e = –N dφ/dt); dynamically induced emf from conductor moving in steady field (e = Blv sinθ). The former occurs in transformers, the latter in generators.

State Faraday's laws of electromagnetic induction. Distinguish between statically induced emf and dynamically induced emf.

Faraday's laws of electromagnetic induction

  1. First law: when the magnetic flux linked with a coil or conductor changes, an emf is induced in it. There is no emf while the flux is constant.
  2. Second law: the magnitude of the induced emf equals the rate of change of flux linkages, e=Ndϕdte = N\dfrac{d\phi}{dt}. The direction is given by Lenz's law, which opposes the cause of the change, hence e=−Ndϕdte = -N\dfrac{d\phi}{dt}.

Statically induced emf vs dynamically induced emf

PointStatically induced emfDynamically induced emf
CauseFlux changes with time while the coil is stationaryConductor moves in a steady field, cutting the flux
Formulae=−N dϕ/dte = -N\,d\phi/dte=Blvsin⁡θe = Blv\sin\theta
MotionNo relative motion neededRelative motion between field and conductor is essential
TypesSelf-induced and mutually inducedSingle type (motional emf)
ExampleTransformer, inductorGenerator, alternator
Direction ruleLenz's lawFleming's right-hand rule
Source of fluxAlternating or varying currentUsually a steady field (dc excitation)

✓ Answer checked by Claude Opus 5.5 (high effort)

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