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DressCritical t1_j6kh5ap wrote

If the current is DC, the current causes all muscles to contract. This closes your hand and prevents you from letting go.

If the current is AC, the muscles spasm, and you probably will let go.

In power stations and such, high-voltage direct current is common, and a short can electrify almost any piece of metal. To protect themselves workers brush the back of their hands against metal objects before using them. This way, if the muscles contract, they will violently remove your hand from the object, not grab it.

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See_Bee10 t1_j6lkcdr wrote

I think you have that backwards. AC causes muscle contractions. If DC did, you wouldn't see videos of people locked on to things that have become electrified, because the power from the plant is AC. That's why Edison electrocuted an elephant.

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DressCritical t1_j6llpv6 wrote

Nope.

AC can induce muscle tetanus, but while it can cause you to lock a hand to something, DC is quite a bit more likely to do so. AC has a greater chance of causing a spasm that either removes the hand or allows the victim to pull free.

AC, however, is more likely to kill you, as it can trigger ventricular fibrillation. DC is more likely to stop your heart, which can actually be easier to recover from.

As for Edison, he electrocuted the elephant and invented the electric chair to illustrate the dangers of AC current. Not because he thought it would be all that dangerous at household voltages, but because he owned the patents on DC and wanted AC to look bad. Look into Edison a bit, you will see that he was something of a jerk.

However, for local grid purposes, AC is much better and won out in the end.

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2MB26 t1_j6kkb2m wrote

How does touching the back of their hand to metal protect them?

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paulmarchant t1_j6kld4p wrote

The theory is that the muscle contraction pulls your hand / arm away from the electrified thing you touched, rather than pushing you on to it.

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travelinmatt76 t1_j6kw4rf wrote

Well the first step is to verify power is off, then check with a meter or detector, then the final step is to use the back of the hand.

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See_Bee10 t1_j6lkwa8 wrote

If you touch with the back of your hand, you might get shocked but when/if your hand locks up it won't grab on to anything. The electricity itself isn't holding you, it just interferes with the way your brain talks to your muscles and you end up holding yourself.

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