A generator is constructed by rotating a coil of N turns in a magnetic field B a

Question

A generator is constructed by rotating a coil of N turns in a magnetic field B at a frequency f. The internal resistance of the coil is R and the cross sectional area of the coil is A. Decide which statements are true and which are false. If the first is T and the rest F, enter TFFFFF.

A) The maximum induced EMF doubles if the frequency f is doubled. B) The maximum induced EMF doubles if the magnetic field B is doubled.

C) The maximum induced EMF occurs when the coil is rotated about an axis parallel to the magnetic field lines.

D) The maximum induced EMF doubles if the resistance R is doubled.

E) The maximum induced EMF doubles if the area A is doubled.

F) The maximum induced EMF occurs when the coil is rotated about an axis normal to the plane of the coil.

Explanation / Answer

Use the equation based on the generator emf E(peak) = B.A.N.?

Where,
(B=field perp. to rotation axis, A=coil area, N=No.of turns on coil, ?=turning ang.vel.)

(A) False. The frequency is independent of the induced EMF (unless you're approaching zero).

(B)  True. You're increasing the intensity of the magnetic field, thereby increasing the intensity of the induced EMF.

(C)  True - max emf when plane of coil is parallel to B (max "cutting" of flux)

(D) False - induced emf has nothing to do with R

(E) False: The maximum induced EMF occurs when the coil is rotated about an axis perpendicular to the plane of the coil.

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