Page 12 - 12-phy-15 ELECTROMAGNETIC INDUCTION

15. Electromagnetic Induction eLearn.Punjab

Example 15.2: A loop of wire is placed In a uniform magnetic field that is perpendicular to the

plane of the loop. The strength of the magnetic field is 0.6 T. The area of the loop begins to shrink
at a constant rate of DA/Dt = 0.8 m s . What is the magnitude of emf induced in the loop while it is
2 -1
shrinking?

Solution:

DA
Rate of change of area = = 0.8m s 1
2 −
Dt

1
Magnetic flux density = B = 0.6T = 0.6NA m − 1
−
=
Number of turns = N 1

Induced emf = e= ?

Df DA DA
o
Rate of change of flux = = B cos0 = B
D Dt t D t

Applying Faraday's Law, magnitude of induced emf

Df DA
e= N = NB
D Dt t

1
1
= 1x0.6NA m x0.8m s 1
2 −
−
−
1
−
e= 0.48JC = 0.48V

15.4 LENZ’S LAW AND DIRECTION OF INDUCED EMF

In the previous section, a mathematical expression of the Faraday’s law of electromagnetic induction

was derived as

Df
e= − N
Dt

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