Fuses and circuit breakers are both devices that 'break' if the current through them is too large.
A fuse is usually a thin piece
of wire that will melt and break the circuit if too large a current flows through it. The thicker
the wire the more current is needed to melt it and the higher the 'rating' of the fuse. The purpose of a fuse is to protect the wiring
and the equipment. If the fuse was not there and something went wrong the wires
themselves would get hot and maybe catch fire. In a plug the fuse is in a glass
tube.
Fuses should also be connected in the live wire you should always switch off
before changing a fuse.
The disadvantage a fuse wire is that it takes a finite length of time for
the wire to heat up and break, and in that time damage may be done to the equipment.
A
circuit breaker is an electronic circuit that will switch off the current if it is too great. Such a circuit is
designed to operate much more quickly than a fuse and so the damage is less because the current
is switched off in a much shorter time.
Circuit breakers are often used to protect the user if
the casing of the equipment becomes live. They break the circuit before the person using the
equipment gets a near fatal shock.