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.

The average induced EMF doubles if the area A isdoubled.
a. True
b. False
The average induced EMF doubles if the frequency f isdoubled.
a. True
b. False
The maximum induced EMF occurs when the coil is rotatedabout an axis perpendicular to area A.
a. True
b. False
The average induced EMF doubles if the resistance R isdoubled.
a. True
b. False
The average induced EMF doubles if the magnetic field Bis doubled.
a. True
b. False

Find the explanations below

a. True

b. False

a. True

b. False

a. True

Explanation:

The EMF is given by :

E = NABwsinwt

where

E induced EMF

A Area

B magnetic field

w Angular velocity

wt phase angle

where w =2π/f

E = 2πNABsinwt/f

The average induced EMF doubles if the area A is doubled.

E ∝  A

a. True

The average induced EMF doubles if the frequency f is doubled.

E ∝  1/f

b. False

The maximum induced EMF occurs when the coil is rotated about an axis perpendicular to area A.

E ∝ sinwt

∅ = wt

at 90 deg

sinwt = sin90=1

a.True

The average induced EMF doubles if the resistance R is doubled.

The induced voltage at zero current does not depend on the resistance of the conductor. As soon as a load is connected to it, the effective voltage measured on the conductor will be reduced by V=IR, though.

b. False

The average induced EMF doubles if the magnetic field B is doubled.

E ∝  B

a. True