Using an ohmmeter, a student measures the resistance between various points on his body. He finds that the resistance between two points on the same finger is about the same as the resistance between two points on opposite hands—both are several hundred thousand ohms. Furthermore, the resistance decreases when more skin is brought into contact with the probes of the ohmmeter. Finally, there is a dramatic drop in resistance (to a few thousand ohms) when the skin is wet. Explain these observations and their implications regarding skin and the internal resistance of the human body.

An object's electrical resistance is a way to measure the flow of electric current. Electrical conductance, which measures the ease with which an electric current passes, is its reciprocal quantity.

When electrons move through a conductor, such as a metal wire, an electric current occurs. The ions in the metal can clash with the traveling electrons. This produces resistance and makes it more difficult for the electricity to flow.

The skin contains more water and salt, which are good conductors. The skin has a far higher resistance than our inside tissue and organs. Because there is more highly conductive tissue just under the skin, the resistance lowers when a bigger patch of skin is in contact with the ohmmeter. (Imagine the skin and the tissue beneath it as series-connected resistors, with their resistances adding up.)

When the skin is moist, water's high conductivity allows more electricity to pass through, lowering resistance. As a result, having dry skin protects us from being shocked.