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Magnetism
Magnetism is a force exerted by magnets. Magnets are objects surrounded by a
magnetic field. A magnetic field is the space around a magnet, in which a magnetic
force is exerted. Every spinning electron is a magnet, most atoms’ electrons spin in
different directions cancelling their magnetic force.
Each magnet has two poles, a north and a south pole. The magnetic poles are one
of the regions on a magnet that produces magnetic forces. Like poles will repel
each other while opposite poles will attract each other.
Electromagnets
As an electric current or moving charge passes through a wire it produces a
magnetic field. This magnetic field around a wire forms concentric circles. A
current-carrying coil of wire with many loops forms an electromagnet. Magnets
moved near—or even inside coils of wire induce (cause) a current in the coil.
Electromagnets can be used as a motor or generator or simply as a magnet that can
be turned on and off.
An electric motor is made when a permanent magnet is used to produce a magnetic
field in a region where a loop of wire is mounted so that it can turn about an axis.
As current passes through the wire, the wire spins as it is repelled and attracted
to the magnet. The motor converts electrical energy into mechanical energy.
An electric generator is a device that rotates a coil of wire in a stationary
magnetic field inducing a voltage in the coil. The generator converts mechanical
energy into electrical energy.
Law of Conservation of Energy
According to the law of conservation of energy, during transformations the total
amount of energy stays the same. Energy can be not be created or destroyed; it
can only change its form.
Energy Conversions
Energy can be changed from one form to another. Changes in the form of energy
are called energy conversions. Whenever energy is converted, some heat will be
released or lost in the process.
Forms of energy are:

Thermal energy (heat)

Light energy

Electrical energy

Sound energy

Kinetic energy (mechanical)

Chemical energy

Nuclear energy

Potential energy
All forms of energy can be converted into other forms, examples include:
o The sun’s energy through solar cells can be converted directly into
electricity.
o Green plants convert the sun’s energy (electromagnetic) into starches
and sugars (chemical energy).
o In an electric motor, electrical energy is converted to mechanical energy.
o In a battery, chemical energy is converted into electrical energy.
o The mechanical energy of a waterfall is converted to electrical energy in
a generator.
o In an automobile engine, fuel is burned to convert chemical energy into
heat energy. The heat energy is then changed into mechanical energy.