A circuit is a path that current electricity or electrons can flow through. Current electricity is a type of human-made electricity. A simple circuit is made out of four parts: the power source, wires, the load, and a switch! A simple circuit works by electrons, which are negatively charged, exit from the negative terminal of the power source. Then, the electrons flow through the wire to the load. The load is whatever is consuming the electricity. The electrons power the load and come through the switch. If the switch is open, no power flows through. If the switch is closed, the power flows through. Then, the electrons flow from the switch to the positive terminal of the power source. That is a simple circuit!
A short circuit is when one of the wires is placed right in the middle of the circuit. That makes it so that there is more current in that extra piece of wire than any other place. Since that place has more electricity, it can heat up and start a fire! That is why we need a fuse. A fuse breaks the circuit when it gets too hot. The fuse melts when it gets hot. This makes it so that the electricity does not flow through!