Types of Circuits - Short Circuits
A short circuit is a circuit in which the electricity has found an alternative path to return to the source without going through an appropriate load. You can demonstrate this easily by taking a fine piece of wire and connecting it to both the positive and negative terminals of a small battery. The wire will heat instantly and probably melt. In most circuits, this high amperage represents a dangerous situation that could cause a fire or electrocute someone.
Consider the circuit shown where the source is the outlet, the path is the extension cord, and the load is the drill. If the wire inside the drill comes loose and touches the other wire, a new path exists where the current can return to the source without going through a load the drill motor. Thus, the name short circuit because the electrons have found a shorter path to take to get back to the source.
Another type of short circuit occurs when some conductive object accidently gets into an overhead power line. If the object touches both the lines at the same time, the electricity has a short circuit path available to return to the source before it goes to the customer's electric service. If the object is connected to the ground, the earth can act as a short circuit path. Additional information about short circuits and electrical safety is covered in the Safety section.