1) It's the current that does the damage, not the voltage. That's why a 20,000 V static shock makes you jump, but doesn't do any harm - there's almost no current involved and the duration is very short.

2) Research has shown that current in the range from 0.007-0.015 A (7-15 milliamps) AC, when passed through the heart, is enough to cause the arrhythmia that was described. DC current will tend to cause the muscles to freeze, stopping the heart, but also preventing a person from releasing the live object. Ground Fault Circuit Interrupters, commonly installed in bathrooms and laundry rooms in new homes, are designed to trip nearly instantaneously (5-10 ms typically) when they detect 5-7 mA of current flowing to ground. Below those levels they may still trip, but it will take longer. this is done because the risk of injury is lower at lower current levels and nuisance tripping of the device tends to make people remove them, increasing the risk of death to anyone using the area.

3) Current levels above 15 mA, up to about 1000 mA (1 A), don't generally do much more harm than the 7-15 mA current. Currents above 1000 mA start to do damage by causing internal burns due to the heating caused by the current flowing through the body's internal resistance.

4) Higher frequency current does more damage. As the frequency of an AC current increases, a curious thing happens called "skin effect". This happens in a copper wire or in any other conductor, including the human body. The current, instead of flowing more or less evenly through the full cross section of the conductor as it does at DC begins to crowd outward toward the outer perimeter of the conductor. The higher the frequency gets, the more intense the crowding at the surface gets. This causes much higher heating at the surface of the conductor than at the core. In the human body, this causes the burns to be through the thickness of the skin and into the outer layers of the muscle. So current that at 60 Hz (North American Power Line Frequency) might make you sore the next day, presuming it didn't kill you, at 400 Hz (aircraft power frequency) might result in severe burns to the skin. As the frequency gets higher the effect increases. Contact with high-power, high-frequency radio transmitter antennas like those found on cell-phone towers (around 1 GHz) can result in severe burns, although the fall from the tower is probably what will kill you.

5) High frequencies can jump air gaps more effectively than DC or power line frequencies, so shocks from high power radio frequency sources are more likely than from low frequency sources or DC.

6) Ground conductors on products and equipment are designed to minimize the touch voltage on the metal surfaces of a product to less than 50 V to help prevent shocks. They also cause the circuit breaker or fuse that protects the equipment to blow very quickly, limiting the time that a person can be exposed to the shock hazard. Don't cut ground pins off power cords, or use 2-pin too 3-pin adapters. You are risking your life or that of someone you love!

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