An open circuit is a connection that is disconnected. This can cut off parts of the circuit, losing some key functions, or it can halt the circuit entirely.
In an open circuit, no current flows since there is no path to the load and ground. In a short circuit the supply voltage is directly connected to ground.
a closed circuit is a complete circuit with no breaks at all, one example:- a closed circuit occurs when you turn the light switch on an open circuit has a physical break in the circuit, which stops...
Generally a circuit breaker (like a light switch) But I guess you could use a resistor of the right resistance If you are talking about the circuit breaker there is an electromagnetic coil in it...