Electromagnetic Induction
Group: Induction
Wong Chun Jie
Leong Qi Dong
Jwa Li Wen
4S2
2012 T3
Introduction
• Current flowing through a conductor produces
a magnetic field
• Can a magnetic field produce a current in a
conductor?
Video
• http://www.youtube.com/watch?v=ITuR3AQA
YI8
• 1:07:50 – 1:10:4`
Theory – Electromotive Force (emf)
A varying magnetic flux produced an e.m.f,
which produces an induced current in a closed
circuit.
Faraday’s Solenoid Experiment
Steps
1. Move magnet into solenoid
2. Leave the magnet in solenoid
3. Move magnet out of solenoid
Variables
Dependent:
(1) Deflection of galvanometer pointer
(2) Direction of deflection
(3) Magnitude of deflection
Independent:
• Pole of magnet
• Number of turns in solenoid
• Strength of magnet
• Cross-sectional area of solenoid
• Speed of magnet being moved in and out
Results
(1) Deflection of galvanometer pointer
• Deflects: magnet is moving in and out of solenoid
• Does not deflect: magnet remains stationary in
solenoid
• Current is flowing through circuit only when the
magnet is moving in and out of the solenoid
Conclusion
• A varying magnetic field produces an e.m.f,
which produces an induced current in a closed
circuit.
Results
(2) Direction of deflection
Action of Bar
Magnet
Direction of
Deflection
Direction of
e.m.f
N-pole inserted
N-pole withdrawn
S-pole inserted
S-pole withdrawn
Right
Left
Left
Right
Anti-clockwise
Clockwise
Clockwise
Anti-clockwise
Conclusion
Lenz’s Law
• The direction of the induced emf, and thus,
the induced current in a closed circuit, is
always such that the magnetic effect always
opposes the change producing it.
• Why oppose?
– In Work, Energy, Power: GPE = KE
– In Electromagnetic Induction: GPE = KE + Electrical
energy
– KE decreases for the conservation of energy
Results
(3) Magnitude of deflection
Increase in
• number of turns in solenoid
• strength of magnet
• cross-sectional area of solenoid
• speed of magnet being moved in and out
Increases deflection – increases emf
N
ΦB
Rate
Conclusion
• Faraday’s Law of Induction
• Where ℰ is the emf
• Induced emf generated in a conductor is
proportional to the rate of change of magnetic
flux vector linking the circuit.
References
• http://physics.tutorvista.com/electricity-andmagnetism.html#close_iframe
• http://en.wikipedia.org/wiki/Faraday's_law_of
_induction
• http://en.wikipedia.org/wiki/Magnetic_flux
• http://en.wikipedia.org/wiki/Electromotive_fo
rce
Thank You