Every electrical circuit must include a "load'' (something to use the
electricity coming from the source). Without this load, the battery would attempt
to deliver its entire power supply from one pole to another. This is called
a "short circuit." All this electricity would take a short cut to ground and
cause a great amount of damage to other components in the circuit by developing
a tremendous amount of heat. This condition could develop sufficient heat to
melt the insulation on all the surrounding wires and reduce a multiple wire
cable to a lump of plastic and copper.
