How are electromagnets used in a relay switch?

Answer 1

Electromagnets are an iron core that is wrapped by thin copper wire many, many times and each end of the copper winding is connected to positive and grounded (negative) side of battery , via a on/off switch. this is called the control, low current circuit. When switch is closed, current flows through the small windings making the iron core a elector magnet. This magnet pulls in contacts to close the power circut, high current circuit to bring power to the motor or other devices that don't need high current all the time. This is typical in a starter motor, where you only need high current when the motor is activated. In this case there is a second winding that holds the high current contacts closed, while the primary(control) winding is opened when the key is released, Thus disengaging the starter motor via a spring.