As already mentioned the fuse is provided in an electric circuit to protect the apparatus connected to it from being damaged due to excessive current. If no fuse or other similar device is provided in the circuit then a dangerous situation would be created on developing of faults such as over load, short-circuit or earth faults. In case of overload, short circuit and heavy earth faults, a heavy current will circuit to flow through the cables or wires, apparatus etc., these will get heated and so damaged. The fire may also break. In case of earth leakage fault, (i.e. on becoming to be alive and at much higher potential above that of the earth. In each case any person coming in contact with the metal body of the apparatus is liable to get an electric shock, even if that is earthed.

The main precaution to be taken while providing fuse in an electric circuits is that it should be provided only in phase or live pole, never on neutral wire. If the fuse is provided on natural wire in place of live wire, then in abnormal conditions through the fuse will blow out but the lamp or other apparatus still remains connected to the live wire and in case or leakage some trouble may arise an cause a considerable damage. In case the earth fault takes place on the neutral wire between lamp and fuse provided in it,  the fuse will below out because the neutral wire is alightly at a higher potential with respect to earth an so the fault current flows through the neutral wire and fuse melts itself. The current will flow through the live wire lamp, natural wire and earth fault, even after fuse has blown out and this may cause serious damage to the wiring, the apparatus connected or building itself. If the fuses of same capacity are provided on the phase wire and neutral wire, then in case of short-circuit, one of them will blow out first. It the fuse on natural wire bellows out first, the fuse in phase wire remains intact and fault apparatus still remains connected to the live. If some person comes in contact with the faulty apparatus. he is liable to get electric shock. In case the installation is connected to 3 phase 4 wire supply system, and fuses are provided on both live and natural wires, fuse on neutral wire blows out, then voltage of each phase to will become considerably different, which is not desirable. Hence the fuse is provided only in phase or live pole, never on neutral wire.

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