Automobile

Electricity is used for many parts of the car, from the headlights to the radio, but its chief function is to provide the electrical spark needed to ignite the fuel in the cylinders. This is performed by an electrical system comprises a battery, starter motor, alternator, distributor, ignition coil, and ignition switch. As discussed above, the starter motor is necessary for generating the power to carry the engine through its initial movements. Initial voltage is supplied by the battery, which is kept charged by the alternator. The alternator creates electrical current from the movement of the engine, much as windmills and watermills generate current from the movement of air or water.

Turning the key in the ignition switch draws current from the battery. This current, however, is not strong enough to provide spark to the spark plugs so it is drawn through the ignition coil, which is comprised of the tight primary winding and the looser secondary winding. The introduction of current between these windings creates a powerful magnetic field. Interrupting the current flow, which happens many times a second, causes the magnetic field to collapse. The collapsing of the magnetic field produces a powerful electrical surge. In this way, the 12-volt current from the battery is converted to the 20,000 volts needed as spark to ignite the gasoline.

Because there are two or more cylinders, and therefore as many spark plugs, this powerful current must be distributed—by the distributor—to each spark plug in a carefully controlled sequence. This sequence must be timed so that the cylinders and the pistons powering the crankshaft work smoothly together. For this reason, most automobiles manufactured today utilize an electronic ignition, in which a computer precisely controls the timing and distribution of current to the spark plugs.