Michael Faraday discovered electromagnetic induction in 1831 through experiments using coils, magnets, and galvanometers. Faraday's Law of Induction states that an induced electromotive force (emf) is generated in a loop of wire when there is a change in the magnetic flux through the loop. The induced emf is proportional to the negative rate of change of magnetic flux through the loop. Lenz's law describes the direction of induced current as opposing the change that caused it. Quantities like magnetic field strength, enclosed area, and angle between the field and loop normal can vary to produce an induced emf.

1. Faraday’s
Law

2. Michael Faraday
• 1791 – 1867
• Great experimental scientist
• Invented electric motor,
generator, and transformers
• Discovered electromagnetic
Induction
• Discovered laws of electrolysis

3. Faraday Law of
Induction
- In 1831, Michael Faraday discovered
that, by varying magnetic field with time,
an electric field could be generated.

4. Faraday Law of
Induction
- Electric current is induced when
there is a change in magnetic field.
- The induced emf ε in a coil is
proportional to the negative of the
rate of change of magnetic flux

5. Faraday Law of
Induction
Quantities which can vary with
time:
• Magnitude of B
• Area A enclosed by the loop
• Angle q between B and loop
normal

6. Faraday Law of
Induction
B
d
dt
 
 

7. Faraday Law of
Induction
𝜺 = −𝑁
𝑑Φ𝐵
𝑑𝑡

8. Lenz Law
An induced current always flows in a
direction that opposes the change that
caused it.

9. Faraday Law of
Induction
A plane circular loop of conducting wire of
radius 10 cm which possesses N=15 turns
is placed in a uniform magnetic field. The
direction of the magnetic field makes an
angle of 30⁰ with respect to the normal
direction to the loop. The magnetic field-
strength B is increased at a constant rate
from B1 = 1 T to B2 = 5 T in a time interval of
Δ𝑡 = 10 s. What is the EMF generated
around the loop?

10. Quiz 1. What are the things that Michael Faraday
used in his experiment?
2. Formula used when there is a given no. of
turns of coil
3. What law is used to determine the direction
of the induced current?
4. – 6. What are the quantities which can vary
with time?

11. Quiz
7. – 8. A UHF television loop antenna has a diameter of 24
cm. The magnetic field of a TV signal is normal to the plane
of the loop and, at one instant of time, its magnitude is
changing at the rate 0.16 T/s. The magnetic field is uniform.
What EMF is induced in the antenna?
9. – 10. A plane circular loop of conducting wire of radius 14
cm which possesses N=10 turns is placed in a uniform
magnetic field. The direction of the magnetic field makes
an angle of 40⁰ with respect to the normal direction to the
loop. The magnetic field-strength B is increased at a
constant rate from B1 = 2 T to B2 = 6 T in a time interval of
Δ𝑡 = 12 s. What is the EMF generated around the loop?

12. Quiz 1. Galvanometer, Magnet Bar, Coil
2. 𝜺 = −𝑁
𝑑Φ𝐵
𝑑𝑡
3. Lenz Law
4. – 6. Magnitude of B, Area A enclosed by the
loop, Angle q between B and loop normal
7. – 8. EMF = - 1.52 mV
9. – 10. EMF = - 0.16 V