First, the fuse is connected in series or parallel

Series circuit in which the current is equal, the role of voltage division. Parallel circuit voltage is equal everywhere, the role of shunt.
General fuse in the circuit is connected in series, the voltage can withstand are relatively small, the normal operating current can only be done very small, plug-in self-recovery fuse can be done at a relatively high voltage. So the recovery fuse is generally connected in series in the circuit, the fuse is not divided into positive and negative poles, there is no DC or AC requirements.

Do fuses have to be used in series in a circuit? There are exceptions. Once there are two fuses connected in parallel, increasing the internal resistance, and then the two parallel fuses connected in series to the circuit, but although theoretically this can be used, but because of the internal resistance of each fuse is a little different, so when the circuit current increases, the internal resistance of the fuse may be the first to disconnect, in this way, the fuse in parallel in the circuit does not play a role in its real. If you want to protect multiple circuits with overload, you can use multiple fuses in series in the circuit.

Second, the fuse is connected to the zero wire or fire wire

Fuse connected to the circuit need to pay attention to, do not connect the fuse in the zero line or ground wire, the correct connection is connected to the fire line, so that in the circuit overload, the fuse can be blown in a timely manner to protect the circuit safety.

If the fuse is connected to the zero line, when the line failure caused by the fuse blown, the line and appliances, although there is no current flow, the appliances do not work, it is only because of the circuit breakers (fuse blown at the resistance of infinity) of the reason, and the line and appliances on the voltage still exists, it will cause harm to people, can not play a role in the protection. Therefore, the fuse should be placed on the fire line, and, zero line is not allowed to install a fuse.