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Is High or Low Voltage Worse?

Though it is current, not voltage, that produces a dangerous electrical shock, high voltages are worse, and more dangerous, than low ones. Below about 50 volts, and through dry skin, little potential for shock hazards exist. Batteries, alternating current adapters and the like produce between 3 and 24 volts, which are safe voltage levels. Household AC outlets deliver 110 to 220 volts and present a shock hazard. Higher voltages are more dangerous, depending on the source.

Harmful Current
- Excessive electrical currents passing through the human body produce a few different harmful effects, such as muscle contractions, burns and heart fibrillation. About 15 milliamps of current to cause pain and muscle contractions, and 500 milliamps, or one-half amp, will stop a human heart in a few seconds. Current varies directly with voltage, so the higher the voltage, the greater the chance of a serious shock.
Skin Resistance
- Dry skin has a substantial electrical resistance; it lowers the risk for shock at a given voltage. It serves as an electrical insulator, preventing the conduction of electricity. Skin resistance drops as it gets wetter, as from water or perspiration, increasing the risk for shock. Through dry skin, it takes much more voltage to feel a shock. For wet skin, a much lower voltage will cause a shock.
Ohm's Law
- A principle of electricity called Ohm's law governs the relationships between voltage, current and resistance in electrical circuits and in the human body. Simply stated, I = V / R, or current equals voltage divided by resistance. Increased resistance lowers the current. Increased voltage raises it. If dry skin has a resistance of one million ohms, it takes 15,000 volts to produce 15 milliamps of current and a serious shock. Wet skin, on the other hand, may have a resistance of 10,000 ohms, producing the same shock with only 150 volts. A common battery's voltage is so low that even wet skin will not receive enough current to produce a perceptible shock.
Current Source
- To deliver a harmful shock, the electrical source must be capable of delivering the harmful current as well as the voltage. Some sources, such as batteries, can produce the current but do not have the necessary voltage. An electrical outlet can deliver 15 amps of current, so its higher voltage poses a shock hazard. Static discharges, like the ones you get from taking off a sweater in winter and touching a metal desk, have voltages in excess of 5,000 volts but have extremely weak currents and do not pose a shock hazard.

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