Sunday, January 3, 2010

16-Electromagnetic Induction

Electromagnetic Induction

Electromagnetic Induction is the setting up, or inducing, of an electromotive force (emf) in a conductor whenever there is a change of magnetic flux linkage.
Magnetic Flux is the product of the magnetic flux density and the area normal to the field through which the field is passing.

φ = BAcosθ, unit of φ is weber (Wb)

One weber is the magnetic flux passing through a plane surface of 1 m2 placed normal to a uniform magnetic field of flux density 1 T.

Magnetic Flux Linkage
in a coil is the product of the magnetic flux passing through the coil and the number of turns on the coil.

Φ= Nφ

Faraday’s Law - the magnitude of the induced emf in a coil is directly proportional to the rate of change of the magnetic flux linking (or cutting) the coil.

Lenz's Law states that the direction of the induced e.m.f. is such that it tends to oppose the flux-change causing it, and does oppose it if induced current flows.

Calculate the magnitude of induced emf using

E= ΔNφ/ Δt = ΔNBAcosθ/ Δt


E = - gradient of φ vs t graph.

Determine the direction of induced current / emf using:

-Lenz’s law

-Fleming’s Right-hand rule for a moving conductor cutting the flux.

-Induced emf works like a battery, the induced current flows from lower to higher potential within the induced emf.

-An induced emf is always produced BUT induced current is produced only I there is a COMPLETE circuit.


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