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

So far we have studied

Electric Fields produced by
stationary charges

Magnetic Fields produced by
moving charges

What happens when Magnetic Fields vary in time?


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.

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