Correcting student misconceptions about the cause and prevention of electric shock.

The physics of electric shock is a topic that is addressed in every general physics text. Invariably, the discussion begins with the effects in humans of externally induced internal electric currents of various magnitudes. The texts are fairly good at describing the physiological effects of these currents, i.e. interference with essential nerve processes that can produce convulsive muscle action, ventricular fibrillation, and respiratory arrest. It is made clear that these internal currents are quite small relative to the currents found in household electric appliances. Most texts then discuss strategies that are employed to reduce the danger of electric shock, i.e. polarized plugs, three-wire circuits with the grounding wire and plug, and ground fault circuit interrupters. However, general physics books under-emphasize two important things when discussing electrical safety. These two things are the magnitude of the voltage difference that will produce a lethal shock and how one can prevent the voltage difference from being applied across the human body. In an informal, admittedly unscientific, survey of well-educated acquaintances, it appears that student misconceptions about electrical safety carry over to adulthood. Comments such as "it's the current that kills, not the voltage," a half-truth demonstrating limited knowledge; "the voltage from a car battery is lethal," a false statement; and "you have to be grounded to get shocked," another untruth; coming from respected college graduates in technical fields, make one wonder if the practical aspects of electrical safety are accurately presented in the textbooks. In this presentation we will suggest some ways of correcting these misconceptions, beginning with a complete definition of electric shock followed by demonstrations illustrating electrical safety.

* Tansil, J.E. Department of Physics & Engineering Physics, Southeast Missouri State University.