What device engages power to the chassis of a motor vehicle?

The ignition switch is the device that engages power to the chassis of a motor vehicle. When the ignition switch is turned to a "on" or "start" position, it allows electrical current to flow from the battery to various components of the vehicle, including the ignition system, fuel system, and other essential electrical systems necessary for the vehicle to operate.

In modern vehicles, the ignition switch often works in conjunction with other systems, including safety features like the key fob or starter button, but its primary function is to control the electrical power distribution throughout the vehicle. It plays a crucial role in starting the engine and activating other necessary electrical functions, which is fundamental for the operation of any motor vehicle.