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 resistance R is doubled.
B) The maximum induced EMF occurs when the coil is rotated about an axis parallel to the magnetic field lines.
C) The maximum induced EMF doubles if the magnetic field B is doubled.
D) The maximum induced EMF occurs when the coil is rotated about an axis normal to the plane of the coil.
E) The maximum induced EMF doubles if the frequency f is doubled.
F) The maximum induced EMF doubles if the area A is doubled.

Explanation / Answer

EMF = NABw*sin (wt)

EMF)max when sin wt = 1

means wt = 90 deg

EMF)max = NABw

A. False

EMF)max is not depend on Resistance, so it will not change.

B-False

Reason if its rotated about axis parallel to the magnetic field lines then sin wt = 0, which will give us zero emf.

C-True

you max EMF)max is proportional to magnetic field, so if B is doubled, EMF)max will be doubled.

D- false.

E- true

EMF)max is proportional to w in the above formula

w = 2*pi*f

so if f is doubled then w is doubled and then EMF)max is doubled.

F- True

EMF)max is proportional to area so if A is doubled EMF)max will doubled.

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