Induced potential and the generator effect: Magnetism and electromagnetism

Induced potential difference

When an electrical conductor moves relative to a magnetic field or if there is a change in the magnetic field around a conductor, a potential difference is induced across the ends of the conductor

Induced current

If the conductor that has had a potential difference induced across its ends is part of a complete circuit, a current is induced in the conductor

The generator effect

When the movement of a conductor relative to a magnetic field causes a potential difference and a current (if part of a complete circuit) to be induced in a conductor

Magnetic field generated by the induced current

An induced current generates a magnetic field that opposes the original change, either the movement of the conductor or the change in magnetic field

How to reverse the direction of the induced potential difference/current

Reverse direction of movement of the magnet or the coil

Factors affecting the size of the induced potential difference/current

Speed of movement, magnetic field strength is increased, number of turns on the coil

Generator

A device that uses the generator effect to convert kinetic energy into electrical energy

Alternator

An electrical generator which produces alternating current (an ac generator)

Structure of an alternator

Consists of a coil of wire rotating in a magnetic field and two slip rings

Sine curve

The potential difference produced by an ac generator follows the shape of the graph obtained for y = sin x

Dynamo

An electrical generator which produces direct current (a dc generator)

Structure of a dynamo

Consists of a coil of wire rotating in a magnetic field and a split ring commutator

Moving-coil microphone

A microphone in which electrical signals are produced when pressure variations in sound waves vibrate a coil of wire inside a magnetic field