A Shock for this Electrical Engineer

The

The electric fence gate handle. Insulator, or conductor?

I earned my B.S. in Electrical Engineering, Magna Cum Laude. That essentially means I know almost nothing about electricity or engineering.

NONETHELESS, I had to set up a simple circuit to keep my cows inside a paddock I made for them. I bought the portable electric fencing materials: a solar powered charger with battery, the electrical wire (polywire), and the posts.

The circuit is made by hooking up the charger’s positive terminal to the single fence wire, and the charger’s ground to a metal rod I hammered into the dirt. The circuit is “open” until a cow touches the wire, then the electrons travel through the cow to the ground and back to the ground rod. That’s the theory.

But I set it all up and the volt meter measured zero volts. I touched the wire and nothing happened. It was not conducting.

EITHER the ground was too dry and sandy, and my thick work boots too insulated, for the electricity to flow through me into the ground, or I was shorting the hot wire into the ground somewhere. For instance, the hot wire could be touching a metal wire on the permanent fence, or touching vegetation.

I checked the wire, and nothing was grounding it, or so I thought. But then I looked at the “gate handle” I had hooked onto the hot wire and to hook it onto the permanent fence. These have a rubber handle so you can grab it, and I thought they were made of two pieces of metal, such that it insulated the hot wire from the permanent fencing.

On a lark, I removed that gate handle and touched the wire. Zap! Ten thousand volts surged from my finger down to my toes and into the ground. It stung something sharp. Turns out those “insuli-grip” gate handles conduct electricity through the insulated grip. Now I know.

I dunno. My parents will probably be disappointed to know I spent four years in college learning differential equations, Maxwell’s equations, digital signal processing, and advanced analog circuits, only to shock myself with an electric fence after ignorantly shorting it. In college, I learned a ton of theory but almost no practice, and certainly no practice on something as low-tech and blue-collar as farming or ranching with electric fences.

Mark it up as just another practical lesson learned on the homestead.

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21 Responses to A Shock for this Electrical Engineer

  1. Tom says:

    When you say “through” the grip, you mean the wire travelling through the hole in the grip, right? You can touch the grip. DON’T touch the wire! :) If you touched only the grip, and it shocked you, then you have a defective handle. As I’m sure some other readers have, I spent most of my young life with those fences. This is why I’m convinced my parents had so many children (to keep the fences going).

    • Devin Rose says:

      Tom,

      Yes it conducts inside the grip since the metal is connected, but the rubber handle insulates from the metal. So touching the rubber works fine–the handle is good. But I see how my statement was ambiguous!

  2. Great story Devin. I moved onto my sisters farm when I was 15. Boy-howdy I remember the first time I touched one of those wires.

  3. Sounds like a lesson for the spiritual life, too!

  4. KristyB says:

    We had an above-ground electric fence for our dog when I was growing up. It ran along the top of his pen because he was really skilled at climbing out instead of digging under. I got shocked a few times and saw more than one snake meet its end along that wire. It’d slither up to the bottom wire, nothing would happen, so it’d continue up to the top wire and if bottom + top or top-only were touched… ZERP!

  5. Kevin Heldt says:

    Devin, I, too, once shocked myself on an electric fence. Though I should note that in my case it was over a decade BEFORE I graduated near the top of my class with my electrical engineering degree. :)

    • Devin Rose says:

      I was hoping you wouldn’t read this post. Any *real* electrical engineer would see right through my ignorance!

      • Kevin Heldt says:

        Ha! Whatever. I’m not good for much beyond 1s and 0s in the digital world. :)

        In my case, I grew up on 8 acres and we had an electric barbed wire fence to keep animals out and it was my brilliant hypothesis (while carrying a pail of water to the doghouse) that electricity wouldn’t travel through metal…

  6. Big Tex says:

    You should have taken a power course in college. ;-) I enjoyed it.

    • Devin Rose says:

      Big Tex, you know power was the one discipline of EE that I eschewed. I know you and my other Aggie buddies took some power classes. That shock showed me my error!

  7. gmart says:

    I’m not sure how this happened since electrical engineers have no potential ;-)

  8. When I first read this I thought, “Watt in the world was he thinking?” But as I continued to read I found that you conducted yourself in a manner befitting someone who is trying to take care of their new ohm.

    I really got a charge out of it, even though I was shocked to learn that a man of your capacity didn’t transform his stored knowledge into application.

    Just thought that I would relay all of that to you.

  9. Kevin Heldt says:

    You have some witty readers, Devin! My favorites were “electrical engineers have no potential” and “you conducted yourself in a manner befitting someone who is trying to take care of their new ohm”. Ha!

  10. A couple of months ago I was checking on the chickens during a thunderstorm. Cloud to cloud lightening and thunderclap struck just at the exact moment that I brushed up against the electric net and got a nasty shock. I just about had a heart attack and thought I was a goner. As soon as the shock wore off and I realized that was not actually traversing the great divide I hoofed it into the house.

  11. AnneG says:

    Devin, did you read the instructions first? Oh, sorry, I forgot. You’re an engineer.