The above equation is not Faraday’s law of induction because it is
not related to the loop. It is useful when a conductor moves in a uniform
magnetic field.
Let us see a few examples on induced emf.
Example 1
The magnetic flux inside a coil of 400 turns changes for each single
turn with time as shown in figure
Determine the maximum induced emf generated
in the coil. Is there any change in induced EMF
from t = 0.1 second to 0.3 second?
Solution: From the given graph, the increase in
magnetic flux through one turn of coil in 0.1 second
is 0.001 Wb. According to Faraday’s law, the
maximum induced emf generated in the coil is given
by,
ε = N Δ Φ /Δt
Substituting the values, we get
ε = 400(0.001/0.1) = 4V
From graph, there is no change in magnetic flux through coil from t
= 0.1s to 0.3s hence no emf is generated.
Example 2
Find the length of the conductor which is moving with a speed of 10
m/s in the direction perpendicular to the direction of magnetic field of
induction0.8T, if it induces an emf of 8V between the ends of the conductor.
Solution: Given that B = 0.8T, v = 10 m/s and ε = 8V.
Using ε = Blv
8 = 0.8(l)(10)
l (length of the conductor) = 1m
Applications of Faraday’s law of electromagnetic induction
Electromagnetic induction is all around us.
You might have seen that, during security check, people are made to
walk through a large upright coil of wire which produces a weak AC
(alternating) magnetic field. If we are carrying any significant quantities
of iron, the magnetic flux linked with the large coil changes and the
induced current generated in coil triggers an alarm.
The tape recorder which we use to listen to songs (or) record voices
works on the principle of electromagnetic induction. It consists of a
Solution: From the given graph, the increase in
magnetic flux through one turn of coil in 0.1 second
is 0.001 Wb. According to Faraday’s law, the
maximum induced emf generated in the coil is given
by,