Motors use electromagnets.
Because magnetism is a force, magnets can be used to move things.
Electric motors convert the energy of an electric current into motion by
taking advantage of the interaction between current and magnetism.
There are hundreds of devices that contain electric motors. Examples
include power tools, electrical kitchen appliances, and the small fans in
a computer. Almost anything with moving parts that uses current has
an electric motor.
VISUALIZATION
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See a motor in motion.
Motors
Page 541 shows how a simple motor works. The photograph at the top
of the page shows a motor that turns the blades of a fan. The illustration in the middle of the page shows the main parts of a simple
motor. Although they may look different from each other, all motors
have similar parts and work in a similar way. The main parts of an
electrical motor include a voltage source, a shaft, an electromagnet,
and at least one additional magnet. The shaft of the motor turns other
parts of the device.
Recall that an electromagnet consists of a coil of wire with current
flowing through it. Find the electromagnet in the illustration on page
541. The electromagnet is placed between the poles of another magnet.
When current from the voltage source flows through the coil, a
magnetic field is produced around the electromagnet. The poles of
the magnet interact with the poles of the electromagnet, causing the
motor to turn.
1
The poles of the magnet push on the like poles of the electromagnet,
causing the electromagnet to turn.
2
As the motor turns, the opposite poles pull on each other.
3
coil of
wire
magnet
shaft
When the poles of the electromagnet line up with
the opposite poles of the magnet, a part of the
motor called the commutator reverses the polarity
of the electromagnet. Now, the poles push on each
other again and the motor continues to turn.
The illustration of the motor on page 541 is
simplified so that you can see all of the parts. If
you saw the inside of an actual motor, it might
look like the illustration on the left. Notice that
the wire is coiled many times. The electromagnet in a strong motor may coil hundreds of
times. The more coils, the stronger the motor.
What causes the electromagnet in a motor to turn?
540 Unit 4: Electricity and Magnetism