Electric motors |
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Imagine a wire carrying an
electric current, placed between two magnets. The magnetic fields from
the magnet interact with the electrical magnetic field from the wire.
The force that results moves the wire to a new position. This is called
"catapult effect". Electric motors
use this idea.
It may help you to understand electric motors better if you build one yourself. You will need:
(The Usborne Book of Science,1993) |
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What is happening? There are two separate fields of force working together in the motor. Imagine the wire carrying the current is sticking straight out of the page towards you. The two magnets, with their opposite poles together, set up fields of force that cross in the space between them (look at diagram 1). Each wire makes its own field of force. (diagram 2). The combined force looks like this (diagram 3). It has a "catapult effect" on the wire, pushing it to one side. In the motor this has the effect of pushing one side of the coil up and the other side down, which means the coil will rotate. Electric motors are used to do many useful jobs of work; in vacuum cleaners, drills, trains, lifts and washing machines for instance. The motor is using electrical energy to do "work" (i.e. drive a machine).
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Click here to see animation of electric motor, and here for Lorentz force.
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