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

Explanation / Answer

EMF = NABw*sin (wt)

EMF)max when sin wt = 1

means wt = 90 deg

EMF)max = NABw

1. False

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

2. True

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

3. 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.

4. False

5. True

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

6. False

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

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