Apart from the
main charging, starting and ignition circuits, there are other circuits that
power lights, electric motors, the sensors and gauges of electrical
instruments, heating elements, magnetically operated locks (if fitted), the
radio and so on.
All circuits
are opened and closed either by switches or by relays - remote switched
operated by electromagnets.
The energy needed to push current through a resistance is
transformed into heat. This can be useful, for example in the very thin
filament of a light bulb, which glows white hot.
However, a component with a high current consumption must not be
connected using wires which are too thin, or the wires will overheat, blow a
fuse, or burn out.
All the electrical units of measurement are interrelated: a
pressure of 1 volt causes a current of 1 amp to flow through a resistance of 1
ohm. Volts divided by ohms equal amps. For example, a light bulb with a
resistance of 3 ohms, in a 12 volt system, consumes 4 amps.
