| For an electric shock to occur, a person must | | | | Ohms, but resistance across other parts of the |
| become a part of an electrical circuit in such a | | | | body can be much higher. There is a wide |
| way that electric current passes over their skin | | | | variation in body resistance between individuals, so |
| or through their body. Under certain conditions, | | | | the same voltage level may result in different |
| even momentary contact with an energized metal | | | | effects. |
| object can result in serious injury and even death. | | | | Most electrical injuries occur from alternating |
| According to an article in the American Journal of | | | | current (AC) at levels above 50 Volts at the low |
| Industrial Medicine: | | | | frequencies typically maintained by electric utilities. |
| "Contact with live electrical wiring, equipment, and | | | | The North American utilities normally generate |
| light fixtures was the main cause of electrical | | | | power at a frequency of 60 cycles per second. |
| deaths and injuries among electrical workers, | | | | The "cycles per second" unit of frequency is also |
| followed by contact with overhead power lines. | | | | referred to as "Hertz," usually abbreviated as "Hz." |
| Among non-electrical workers, contact with | | | | At 60Hz frequency, the threshold for perception |
| overhead power lines was the major cause of | | | | occurs with electrical currents as low as 0.0001 |
| death. Other causes included contact with | | | | Amps. The "can't let go" electrical current for |
| energized metal objects, machinery, power tools, | | | | adults is approximately 0.010 to 0.015 Amps. This |
| and portable lights." | | | | is the current that causes involuntary muscle |
| From an engineering viewpoint, the body's | | | | contractions severe enough to prevent the |
| electrical resistance is an important variable. | | | | person from letting go of the source of the |
| Electrical resistance of an object is a measure of | | | | electrical shock. |
| how freely electrical current can flow across the | | | | Electric currents as low as 0.050 Amps at 120V, |
| object when a voltage is applied across it. | | | | 60Hz, have been known to cause death. Just to |
| Resistance is measured in units called "Ohms." | | | | give you an idea of how small that current is... a |
| Resistance of a person's body can depend on skin | | | | table lamp with one 40 Watt incandescent bulb |
| dryness, perspiration level, thickness of the skin, | | | | draws 0.333 Amps from a 120 Volt, 60 Hz |
| the distance that the electrical current travels | | | | household electrical outlet! In the interest of |
| through the skin, and other factors. The typical | | | | electrical safety, the National Electrical Code (NEC) |
| human body has a hand-to-hand electrical | | | | considers 0.005 Amps at 120V, 60Hz to be the |
| resistance somewhere between 1,000 and 2,000 | | | | safe upper limit for children and adults. |