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Electromagnetic induction facts for kids

Kids Encyclopedia Facts


Electromagnetic induction is where a voltage or current is produced in a conductor by a changing magnetic flux. It may happen when a magnet is moved in a solenoid, thus changing the magnetic flux.

Magnetic flux

When a coiled wire is introduced near a magnet, the magnetic lines of force pass through the coil. This causes the magnetic flux to change. Magnetic flux is represented by the symbol {\Phi}, therefore we can say that {\Phi} = BAcos(a) and the resulting unit will be Tm^2, where T is the unit for magnetic field and m^2 is the unit for area.

The changing magnetic flux generates an electromotive force (EMF). This force moves free electrons in a certain way, which constitute a current.

Faraday's law

Michael Faraday found that an electromotive force is generated when there is a change in magnetic flux in a conductor.

His laws state that:

\mathcal{E} = {-{d\Phi} \over dt}

where,

\mathcal{E} is the electromotive force, measured in volts;

{d\Phi} is the change in magnetic flux, measured in webers;

dt is the change in time, measured in seconds.

In the case of a solenoid:

\mathcal{E} = {-N{d\Phi} \over dt}

where,

N is the number of loops in the solenoid.

Lenz's law

The negative sign in both equation above is a result of Lenz's law, named after Heinrich Lenz. His law states that the electromotive force (EMF) produces a current that opposes the motion of the changing magnetic flux.

Related pages

Images for kids

  • Electromagnetic induction - solenoid to loop - animation

    Alternating electric current flows through the solenoid on the left, producing a changing magnetic field. This field causes, by electromagnetic induction, an electric current to flow in the wire loop on the right.

  • Induction experiment

    Faraday's experiment showing induction between coils of wire: The liquid battery (right) provides a current that flows through the small coil (A), creating a magnetic field. When the coils are stationary, no current is induced. But when the small coil is moved in or out of the large coil (B), the magnetic flux through the large coil changes, inducing a current which is detected by the galvanometer (G).

  • Solenoid-1

    A solenoid

  • Spindle

    Rectangular wire loop rotating at angular velocity ω in radially outward pointing magnetic field B of fixed magnitude. The circuit is completed by brushes making sliding contact with top and bottom discs, which have conducting rims. This is a simplified version of the drum generator.

  • Current Clamp

    A current clamp

See also

Kids robot.svg In Spanish: Inducción electromagnética para niños

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