What is an automotive relay?

Answer 1

An automotive relay is a device that uses a small amount of current to control a large current-drawing device. For example; using a small switch on your dashboard to run the starter motor on your car. The starter motor on your car is probably the largest draw of electricity from your battery. When you need the electricity from your battery to start your car, you have to control that flow of electricity somehow. In the early days of electricity (automotive-related), the designers used a large wire or cable to allow that high flow of energy from the battery to your starter-motor. This became very impractical because of the excessive size of the wiring and switches needed to run that motor. Also, the longer the wire needed to run that device, the more drop in current and voltage would occur. Hence, another source of starting problems could surface. As technology improved, so did the devices to control the flow of electricity. The relay was born! Inside the relay is a small electromagnetic coil which again, uses the small amount of electricity from that small ignition switch on you dashboard or steering column to close a set of electrical contacts inside the relay. These contacts close allowing the large amount of electrical current to flow from your battery to the starter motor, without having to have the large wires inside the car, avoids the unnecessary length of those wires and provides the shortest path of that high-current electrical power to flow from your fingers to the starter! This is just one example of a relay's use, you can substitute any large electrical device for the starter motor, automobiles can have dozens of electronic and electro-mechanical relays!