What acts as an electromagnetic switch between the ignition switch and starter motor?

The solenoid functions as an electromagnetic switch in the context of automotive systems, specifically between the ignition switch and the starter motor. When the ignition switch is turned on, it sends a low current signal to the solenoid. The solenoid then uses this signal to create a magnetic field that closes a set of contacts, allowing a high current to flow directly from the battery to the starter motor. This process effectively starts the engine by engaging the starter motor to turn the engine over.

Considering the other choices, while a relay also acts as a switch but is typically used for lower current applications and in different contexts; a fuse serves to protect electrical circuits from overloads rather than facilitating the connection between components; and a transistor is a semiconductor device that can amplify or switch electronic signals but is not used in this specific application of engaging a starter motor.