Figure 15 Even a small current in your body can cause a painful shock or injury. Analyzing Data What is the lowest level of current that causes serious injury?

Insulation also prevents short circuits. In a short circuit, current finds a short path through the circuit with less resistance than the full path through the circuit. A three-prong plug can prevent shocks caused by short circuits. In Figure 15 you can see the circular third prong, which connects to ground. These plugs are used on devices with metal exteriors, such as an electric drill. If a short circuit develops, you might get a shock by holding the drill. But instead of entering your body, the current takes an easier path to ground through the grounding wire. The transfer of excess charge through a conductor to Earth is called grounding.

A ground-fault circuit interrupter (GFCI) like the one shown in Figure 15 is an electrical safety outlet. It monitors current flowing to and from an outlet or appliance. If these two currents are not equal, it means current is escaping. The GFCI opens the circuit to prevent serious electric shocks.

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