Question

what is main use of solenoid

Answer 1

Solenoids are most commonly used as electromagnets, and all the examples so far are that kind of solenoid. But there are some other uses. They can be used to slow the flow of electricity in a circuit, making them an example of an inductor, or an impedance device.
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Answer 2

They can be used to slow the flow of electricity in a circuit, making them an example of an inductor, or an impedance device. Cars also have a type of solenoid that is really just a motor that happens to work using a coil of wire. The job of the solenoid is to turn electrical energy into movement.
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