The three states of the circuit are mainly: path, breaking circuit, short circuit.
Path: Current flows through the load in the circuit
Breaking circuit: no current in the circuit
Short circuit: no load in the circuit
It is worth noting that if the circuit is short-circuited, the current I is very large. If there is no protection device in the circuit, the large short-circuit current can easily cause the line to overheat or burn out the power supply directly, causing serious safety accidents or property damage. It should be careful of electrician work. Therefore, it needs to install a fuse device (such as a fuse) in the circuit, which can instantly burn out the fuse when the current suddenly increases. It is ensure a circuit break and protecting the safety of the equipment and power supply.