Question

role of fuse. How is the fuse connected in a circuit?

Answer 1

A fuse is nothing more than a short length of wire designed to melt and separate in the event of excessive current. Fuses are always connected in series with the components to be protected from overcurrent, 

Answer 2

The main role of a fuse in a circuit is to save the whole circuit when the rate of current is very high.
It is connected to the wire in the circuit.
It is a small and thin wire which can easily be melt on high current flow thus the fuse melts and the circuit breaks and the whole will safe of high current flow.

Hope it helps.