Faradays Law

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