At the barn, we have electic wires on some of the fences. I keep seeing dragonflies happily land on them. How are they not getting shocked? Is there a certain pressure required to make the electic fence shock?
In order to get shocked by an electric fence you have to provide a path to ground for the electricity. Also, electric current will always take the shortest path, in this case it’s shortest path is to continue through the fence wire and ignore the dragonfly perched atop.
Same reason birds don’t get shocked when they perch on powerlines. The dragonflies aren’t grounded.
You could touch the electric fence without getting a shock too…as long as no part of your body touched anything else while you were touching the wire. If your feet touch the ground…zzzzap!
Yep… anyone want to try a tightrope act? 
(NB, you really wouldn’t want to slip and land with one leg either side and your feet on the ground… :eek: )
Seriously, in response to the OP - just think for a moment - where could the current go in order to shock a dragonfly sitting on the wire?
So, remember the part in the original Juassic Park when the guy and the two kids climb over the electric fence while the power is shut off. The guy and the girl make it over the fence but then the power comes back on while the boy is still clinging to the top. Sparks fly and the kid flys off the fence.
Shouldn’t the kid have been fine, climbed down till he was about 2 feet from the ground, then jumped through the air hit the ground and be fine?
This may be a stupid question, but aren’t powerlines insulated? I always thought they were. I never made a habit of getting terribly close to them.
From what I understand powerlines are coated to help prevent corrosion, but are not insulated.
Yes they are, but mainly by air which is an excellent insulator. I read that in “Why things are?”, a sort of Cecil-lite column.
Re the Jurassic Park electric fence.
The trouble is that the kid was probably touching more than one wire. Then you get a short circuit. Large birds can sometimes have fatal shocks if they brush two wires at once.
Wanna have some fun? Touch the dragonfy. You’ll have to be stealthy, sure, but it’s worth it…
It’s called “Shaking hands with Jesus!”
:smack: :smack: (didn’t think of that)
It depends on how the fence is wired. They could put a voltage between the wires. Or they could have all the wires at the same voltage and run the return through ground. But mainly it is a movie so they probably did not put any time at all into thinking if this was really how electric fences worked.
I know that many will consider this nitpicking, but if I had a nickle for every time this old saw led to lay confusion…
Electric current does NOT take the shortest path, nor does it take the path of least resistance. It divides in inverse proportion to the resistance of the paths available.
Thus if one path offers oders of magnitude less resistance, then MOST of the current will take the low resistance path, but some will still flow in the high resistance path.
It is not uncommon for the lowest resistance path to be physically longer than a high resistance path. A 100’ long copper wire to ground will prevent you from shock when touching an electric fence.
'Cause dragonflies don’t pee.
[hijack]
A family friend was visiting the place during a weekend when we put up an electric fence so the horses could enjoy the nice grassy lawn and we could save having to mow the lawn. The friend, an elderly lady, who just happened to have very dry skin held out an apple for the horses. What she did not realize was that her forarm was pressed against the fence. The horse, unwittingly, found out when he bit into the apple.
[/hijack]