Short circuiting: Whenever live and neutral wires come
in contact with each other, the incident is called short circuiting. In
this case, resistance of a circuit decreases to a very small value. The
decreasing of resistance increases the current. Due to this increased
current, the wires get heated. This extreme heat may cause fire in the
building.
Overloading: Every supply has a capacity to bear a
maximum load, i.e., the power that can be supplied has a limit.
Sometimes, the number of appliances which are switched on at the same
time have power more than the capacity of the line. This is called
overloading. In this situation, wires of the supply get heated due to
extremely large current flowing through them and the circuit may catch
fire. To avoid this fire, we use an electric fuse in the circuit.