7.1.1 Lecture on Safety
Probably the most hazardous thing in electronics is your household line voltage, around 120 V at 60 Hz in the United States (240 V at 50 Hz in many other countries). What often happens is an ungrounded metal object comes in contact with a hot wire, and then you touch the "hot object," discovering in the process that your body acts as a conducting medium for current to flow to ground. (The ground and ground wires are, in effect, at the same potential as the neutral wire—they are tied together at the utility box.) The frequency and amplitude of the line voltage tend to be at the perfect levels for inducing involuntary muscle contractions that prevent you from letting go of ...