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Section 8 - 3
Transformers and Charges in Magnetic Fields
Atoms in a magnet are aligned according to their magnetic domains.
Electromagnetic Induction is the production of a current in a
conducting circuit by a change in the strength, position, or orientation
in an external magnetic field. This is the reason generators and electric
motors work. In an AC generator, when charges experience the
maximum magnetic force, the current increases. Also in an AC
generator, the magnitude of the current produced depends on the
orientation of the loop in a magnetic field. The current is at a
minimum when the loop is perpendicular to the magnetic field. The
amount of current produced will vary with time.
Pushing a magnet through an electric field requires work. The greater
the electric field, the stronger the force required to push the magnet
through the electric field. When a charge moves along or opposite the
direction of the magnetic field lines, the magnetic force is zero. When
a wire is moving perpendicular to a magnetic field, the force on the
charges is at a maximum. When a wire is moving parallel to a
magnetic field, no current is induced in the wire.
Transformers are devices that can change one alternating current
voltage into another alternating current. Transformers can increase or
decrease voltage. They change both the amperage and the voltage of
an electric current – when one increases, the other decreases. There are
two coils of wire inside a transformer. The primary coil uses the input
electricity. The secondary coil creates the output electricity.
In a step-up transformer, the number of turns of wire is greater in the
secondary coil than in the primary coil, and the output voltage exceeds
the input voltage.
In a step-down transformer, this is the opposite.