Download Magnetism Magnetism is a force exerted by magnets. Magnets are

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.
Energy Flow Diagrams
Energy flow diagrams show how energy is transformed as it moves through a
system. Accounts for the thermal energy (heat) given off during that
transformation.
Light bulb 
Car Engine 
Microphone 
Photosynthesis 
Energy efficiency
Useful energy is transferred to where it is required in the form that it is wanted.
Other forms of energy are referred to as ‘wasted’ or given off in the form of heat.
Strategies to reduce this heat loss are intended to improve the efficiency of a
device. Energy efficiency is a measure of how usefully energy is converted by a
device.
Energy efficient light bulbs are designed to produce more useful light energy for
the same amount of input electrical energy by wasting less energy to heat. Use of
energy efficient light bulbs is one strategy to conserve or reduce our consumption
of energy. Within our homes there are many strategies we can use to conserve
energy.