In order for a circuit to operate it must form a complete loop: there has to be a connection between the power source, the switch and the electrical appliance. Electricity flows from the positive power source terminal and returns to the negative power source terminal. While the circuit is complete, electricity flows and the appliance operates. To isolate a circuit, you need to terminate the flow of electricity through it.
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Decide whether you want to isolate a complete circuit or a particular electrical appliance. For example, all the wall sockets in your home are connected using a wiring method known as parallel or ring wiring. Parallel wiring forms a complete circuit as it starts and returns to the fuse box. However, each wall socket runs independently off the main circuit and this means you can isolate individual electrical appliances that connect to a wall socket.
Flip the trip switch or remove a fuse in your fuse box by hand if you want to completely isolate a circuit such as the lights or wall sockets. Open the fuse box cover to see a line of switches that can move up or down. If you get an electrical short in one of your circuits the appropriate switch trips and turns off the electricity supply. Trip switches are easy to reset as you simply move the switch to the "On" position. Each trip switch or fuse is connected to a different circuit and is clearly labeled. Flipping the trip switch to the "Off" position or removing a fuse isolates all electricity to your chosen circuit and makes it safe to work on.
Isolate electricity to a particular electrical appliance by turning the switch on the wall socket to the "Off" position. By doing so you won't need to trip the switch or remove the fuse that connects the circuit to all the wall sockets. Remove the plug from the wall socket so you are certain electricity to the appliance is isolated. You can continue to use electrical appliances connected to other wall sockets as you haven't flipped the trip switch or removed the main fuse.