Most cars are a machine centered around an internal combustion engine. The engine produces power, which turns drive shafts that turn wheels and give the car motion. A steering wheel connected to the front axle allows the driver to control the car, while brakes bring the car to a stop. A car also relies on a battery to run various functions such as heating, cooling, power steering and radio.
The explosion of the fuel within an internal combustion engine turns a crankshaft, which in turn rotates the drive shaft. The transmission uses gears automatically or manually to determine the velocity at which the drive shaft spins. The accelerator introduces more gasoline to the engine, which creates more power and thus more speed. The brake pedal applies friction to brake discs or drums attached to the axles and slows the car down. Although they were purely mechanical at their inception, as of 2014, many of these systems are electronically or hydraulically activated.
The battery is an integral part of a car's operation. It provides the spark to the internal combustion engine and power to the different systems that require electricity. Some cars have electric motors rather than internal combustion ones, which means the car relies on the battery for all of its functions.