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Faraday's Law of Induction
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The Electric Universe, by David Bodanis
Dr. Walter Lewin (MIT)
Electromagnet Induction.mov (106 MB)
Michael Faraday
1791-1867



So far we have studied


Electric Fields produced by
stationary charges

and
Magnetic Fields produced by
moving charges


What happens when Magnetic Fields vary in time?

wmv



What is
ElectroMagnetic Induction?

Why was Faraday's discovery so important?

Faraday's Experiment

An electric current can be induced in a circuit by a changing magnetic field

click on the switch




The induced emf in a circuit is directly proportional to the time rate of change of the magnetic flux through the circuit.







Watch the magnet as it enters the area of the super-cooled copper ring and as it leaves.
MIT



Mechanical Universe

Faraday and the Law of ElectroMagnetic Induction

 
Lenz's Law
The induced current in a loop is in the direction
that creates a magnetic field that opposes
the change in magnetic flux through the loop.


Faraday's and Lenz's Law




Faraday's Law and Terminal Velocity


Electric Motors and Generators (click on diagrams)
MIT ElectroMagnetism Animations





Why does the metal ring jumps off the center post?



Is Faraday's Law in play here?


Is it because of Lenz's Law or is there another principle at play here?








Hybrid Cars and Regenerative Braking
The greatest benefit of the gasoline engine is


the high energy density of gasoline, on the order of 12,000 Wh/kg,
in contrast with the much lower energy density of batteries, on the order of 500 Wh/kg.

This allows the much greater range of vehicles run on gasoline engines. The benefits of electric motors include high torque at low speeds, the absence of on-board emissions, and regenerative braking.
-- Karen Burke

Eddy Currents
Mechanical Universe
Maxwell's Equations


Gauss's Law




Gauss's Law of Magnetism





Faraday's Law




Ampere-Maxwell Law





Lorentz Force Law




Quick Quiz 31