Ch-06 Electromagnetic
Induction
Lect-01
Today’s Goal
Farraday’s Law
Lenz’s Law
Magnetic Flux:
Magnetic Flux through any surface held in a magnetic
field is measured as the total number of magnetic field
lines crossing the surface. It is a scalar quantity.
In a Non-uniform Field
Flux through Coil of N turns
FARADAY’S LAW OF ELECTROMAGNETIC INDUCTION
First Law: Whenever there is a change in magnetic flux
linked with a conductor, an EMF is induced in the
conductor.
Second Law: Magnitude of the induced EMF is equal to
the Rate of change in Magnetic Flux.
How Flux can change:
Q) The magnetic flux through a coil perpendicular to the
plane is varying according to the relation: 𝛟 = (5t3+4t2+2t5)Wb. Calculate the induced current through the coil at t=2 s,
if the resistance of the coil is 5Ω .
a)
b)
c)
d)
10.2 A
11.4 A
15.6 A
18.2 A
Q) A coil of area 0.04 m2 having 1000 turns is suspended
perpendicular to a magnetic field of 5.0x 10-5 Wbm-2 . It is
rotated through 90o in 0.2 s. Calculate the average emf
induced in it.
a)
b)
c)
d)
0.1 V
0.01 V
1V
10 V
Q) A conducting circular loop is placed in a uniform Magnetic
Field such that it’s plane is perpendicular to the field having
strength 0.5 T. If the radius of the coil decreases steadily at
the rate of 10-2 m/s. What will be the magnitude of induced
EMF when Radius of coil is 7 cm.
a)
b)
c)
d)
4.4 x 10-3 V
4.4 x 10-4 V
2.2 x 10-5 V
2.2 x 10-3 V
Induced Charge:
Q) A small coil is introduced between the poles of an
electromagnet so that its axis coincides with the magnetic
field direction. The number of turns is n and the cross
sectional area of the coil is A. When the coil turns through
180o about its diameter, the charge flowing through the coil
is Q. The total resistance of the circuit is R. What is the
magnitude of the magnetic induction?
a)
b)
𝑸𝑹
𝒏𝑨
𝑸𝒏
𝟐𝑹𝑨
c)
d)
𝟐𝑸𝑹
𝒏𝑨
𝑸𝑹
𝟐𝒏𝑨
Q) In a coil of resistance 100Ω , a current is induced by changing
the magnetic flux through it as shown in the figure. The
magnitude of change in flux through the coil is
a)
b)
c)
d)
225 Wb
250 Wb
275 Wb
200 Wb