Appliances that operate either with batteries or by plugging into the household wiring usually come equipped with an AC /DC switch. If switched to AC, the appliance uses electric power that flows back and forth or “alternates” at a (U.S.) rate of 60 cycles per second (60 hertz, or Hz). If DC (“direct current”) is chosen, current flows one way from the batteries to the appliance. AC fields induce weak electric currents in conducting objects, including humans; DC fields do not, unless the DC field changes in space or time relative to the person in the field. In most practical situations, a battery-operated appliance is unlikely to induce electric current in the person using the appliance. Induced currents from AC fields have been a focus for research on how EMFs could affect human health.
