General Question

Poser's avatar

What is the voltage/amperage of an electric fence?

Asked by Poser (7805points) June 16th, 2009 from iPhone

The kind used on farms. My mother just told me about two separate times she was electrocuted by these fences while growing up on a farm. She seems no worse for the wear, but she describes being “stuck” to the fence when the electricity caused her muscles to contract uncontrollably. How much electricity is required to cause this type of reaction?

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14 Answers

sandystrachan's avatar

Is it not something low like 12V or 24V .
Ok according to website its alot more than that 2000 V to 10,000 V .

jeffgoldblumsprivatefacilities's avatar

I think you should find out by peeing on it.

sandystrachan's avatar

Didn’t Mythbusters and Brainiac both bust that myth?

FiRE_MaN's avatar

yes the mythbusters did. and it probably depends on the fence you could change how much is going through it.

DarkScribe's avatar

Voltage is immaterial, it is current that kills or does damage. Usually the fences that I have experience of have a moderate (60/90) voltage and are current limited to a few milliamps. Twelve or twenty-four volts won’t even tickle you, it is too low. Anyone can grab both terminals of a vehicle battery.

Poser's avatar

@DarkScribe So would 60–90 volts be enough to cause someone’s muscles to contract to the point that they couldn’t relax them enough to let go of the fence? I guess it would make sense that the voltage would be fairly high but the current would be kept low. The fences are designed to simply keep the livestock away—not kill them.

Lupin's avatar

I’ve got one. The operating power and voltages range considerably. There are two main kinds. There is the typical homeowner type the pulses about 1 per second with a very short hit of about 500 volts They only draw about 10 Watt continuous so if the pulse is about 50 ms the current can’t be more than than a few milli aps. Think electric grill sparker. It’s a quick snap! Ouch!
The other type (this it the type I have) is called a weeder. The pulse is much longer 250 to 400 ms, pulses every three seconds and has higher power 100W so it can actually burn the grass and cut it off when it touches. That way you don’t have to keep going out in the field and cutting it back. All of the fences pulse so you don’t waste electricity. (Farmers are a thrifty lot.) If you held on to a weeder it would seem like forever but it would still stop.
In 10 years I have found only one dead rabbit near the fence.

Lupin's avatar

I just looked up fences. My, have they changed! Mine is 30 years old. Now there is solar powered, polytape, dog safe, garden fencing. The ancient unit I have is good for 1/4 mile loop to enclose cattle. (I don’t have any.)

DarkScribe's avatar

@Poser So would 60–90 volts be enough to cause someone’s muscles to contract to the point that they couldn’t relax them enough to let go of the fence?

It isn’t a DC fence, it pulses on and off. The type that I have experience with are security, not animal control, and they can certainly make you jump. Pretty much like a an electronic muscle stimulator as used for body toning. They don’t hurt badly and certainly can’t kill. If you are expecting it, you can hold it and not react, great fun for playing practical jokes. Some people can hold onto a car spark plug, the old Kettering system. That is a few thousand volts. It depends on individual skin resistance.

Poser's avatar

Well this would’ve been back in the late 50s, when my mother was just a child. She said the fence had a relay that was supposed to make it pulse on and off, but on this particular fence, it was broken. She didn’t know the voltage, but it was enough that her muscles wouldn’t respond and allow her to release the fence when she accidentally grabbed it.

Lupin's avatar

Mine has that relay in the bottom. And it did indeed burn out a couple of times. It cost me $15 at Agway for a replacement a long time ago.
Did your grandparents (I’m assuming grandparents) have a long fence? I’d guess it was a weeder type. Safety was not an issue then and they didn’t have weed whackers to clear the brush away. It is much easier to let the fence do the job. The unit could easily have had a 20:1 AC transformer that bumped up the 110 volt AC to 2200 VAC. You’d switch it with a relay and current limit it with a resistor.
On breezy nights I could see the glow where the grass was burning off as it touched the wire.

28lorelei's avatar

It is possible for this to happen. However, the danger of electricity is caused by high amperage, not high voltage. Ok, voltage does affect the current but if the resistance is high enough, the current will be low enough not to be dangerous. Current can be derived from the following formula:
V=IR where V is voltage, I is current in amps and R is resistance in ohms.

In Texas, apparently some nutcase electrified his fence to 20As, and a six-year-old died because she touched the fence. Usually, though the amperage isn’t more than 10µAs, which will only cause a mild shock.

If the current is more than 10 mAs, muscles contract uncontrollably.
more than 20 mAs, breathing may become labored
death zone is around 100–200 mAs because of heart fibrillation
more than 200 mAs, heart stops beating, may be possible to revive patient

Poser's avatar

Wow, I forgot I asked this question. I don’t get on here a lot anymore. Great answers, though. Thanks!

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