Purely academic questions about electric fence

[vavet]

Our recent trip to universal studios Florida and the “warning” signs around the velociraptor cages got me wondering about electric fences.
how do they work?
it seems there is a voltage potential in the fence wires. The other side of the transformer is put into earth ground. If a human or other animal touches the electrified wire, they complete the otherwise open circuit and the low current runs through their body between the point of contact with the fence and the earth.
sounds good….but not all shoes are conductive, right?
if I was to walk up to it, stand on a piece of wood, and grab the fence wire with one or both hands, then I would feel nothing, right?

Something tells me my understanding is a bit off.

 

[LOW1]

Our recent trip to universal studios Florida and the “warning” signs around the velociraptor cages got me wondering about electric fences.
how do they work?
it seems there is a voltage potential in the fence wires. The other side of the transformer is put into earth ground. If a human or other animal touches the electrified wire, they complete the otherwise open circuit and the low current runs through their body between the point of contact with the fence and the earth.
sounds good….but not all shoes are conductive, right?
if I was to walk up to it, stand on a piece of wood, and grab the fence wire with one or both hands, then I would feel nothing, right?

Something tells me my understanding is a bit off.

When I was a kid I saw my brother pee on an electric fence. That would be the only proper way to test your theory.

 

[larry_g]

First consider that the animals that electric fences are ment to control do not wear shoes. You are correct that if your insulated from the ground path then you will feel no current flow. The fence charger is like a distributor and coil setup for a spark plug. The current is not constant but pulsed and controlled by somthing that makes and brakes the current flow through the coil. Our old fence charger looked like electric meter and had a glass vial in it that rocked back and forth with a bit of mecury in it that made the contact as it passed the probes in the vial making and breaking the circuit. As a kid it thought it was magical to see the spark it made.

lg
no neat sig line

 

[Shiftless]

The last time I touched an electric fence, I was wearing rubber soled shoes and I definitely got a shock.

 

[rattle_snake]

High voltage will arc across a gap....

 

[lzenglish]

When I was a kid I saw my brother "pee on an electric fence".

And I thought I was the only one who ever took that Dare while walking home from Grade School. It felt like a barbed rod was shoved Waaayyy up my dipstick.

Thanks for bringing that painful memory back. lol........

LZ

 

[wyliesdiesels]

The last time I touched an electric fence, I was wearing rubber soled shoes and I definitely got a shock.

High voltage will arc across a gap....

have to be wearing shoes that are rated for the voltage... the rubber soled shoes werent rated for the fence voltage...

 

[scooby074]

7kv+ will still shock yaeven with rubbersoles , lol. Plus the leaves of grass etc providing alternative pathways.

Circuit is basically + side of the fencer to the wire, - To a ground rod.. when u touch the wire, current goes through your hand, body, to ground.

Funny thing is when you touch the wire between pluses and dont get a shock, so u go back and touch it again but hold your hand there morefirmly "to check the fence". Then the damn thing fires lol

 

[nadogail]

Electric Fences have no need to be physically strong; it may be a shocking revelation, you can trust me on that.

 

[75gmck25]

IIRC, the pulsing of voltage in an electric fence is required for safety purposes. It gives you the chance to pull your hand back off the fence, instead of "freezing" your muscles in a contraction that keeps you in contact.

 

[larry_g]

Electric Fences have no need to be physically strong; it may be a shocking revelation, you can trust me on that.

You obviously have not had fence torn up by deer. Sorry, but trust in your statement is low.

lg
no neat sig line

 

[mm08822]

The last time I touched an electric fence, I was wearing rubber soled shoes and I definitely got a shock.

A lot of that will depend on the moisture content. Walking up on an efence early morning with the due all over your shoes and pants will light you up.
In a tumbleweed, dust-bowl pasture in mid-afternoon is probably not so bad.

As a kid, I remember having contests to see who could hang on the longest. I wonder how many of us today would croak!!

 

[mm08822]

And I thought I was the only one who ever took that Dare while walking home from Grade School. It felt like a barbed rod was shoved Waaayyy up my dipstick.

Thanks for bringing that painful memory back. lol........

LZ

That was the old-school way of checking your electrolyte level.

Getting lit up on the ear while climbing through was just as bad.....poor man's shock therapy.

 

[paulsomlo]

If I was to walk up to it, stand on a piece of wood, and grab the fence wire with one or both hands, then I would feel nothing, right?

I don't believe that's correct - as larry_g mentioned, the high voltage is created by making and breaking the current to a transformer, what's known as a "flyback" circuit. You don't need conductivity to receive a shock because your body has enough capacitance to ground to allow current to flow.

If your supposition were correct, you'd be able to stick your finger in an electrical receptacle (only 110V) while wearing sneakers and not get a shock.

 

[MBfreak]

The "shock" from an electric fence is a sharp peak of several kV. Very short. So you will not need and ohmic conduction thru your shoes.
A capacitor between the sole of your feet thru a dielectric( like a capacitor) shoe to ground will conduct the short peak thru your body.
Certainly not a dangerous current peak, but it will rattle you.

Ola