Electric fence…what happens

What happens when grass touches energized fence wires?

Think of the wires as pressurized with excess electrons from the energizer's pulse. 

Green vegetation is a conductor—particularly when wet. When it contacts and energized wire, energy is pushed through the moisture in the stem into the soil. This is often called a "leak" (similar to a hole in a water hose) or a "short." 

In short—grass leaks electrons from the fence. However, if the energizer's pulse (joules output) is large enough, it can cope with the loss due to grass contact (overcoming weed-load). 

What happens when an animal touches the energized wires?

The high voltage of the pulse pushes electrons through the animal's point of contact (often nose or ears) then through the body's tissue and fluids and out through the feet/hooves/paws into the soil moisture. 

Is the animal's weight a factor?

The weight of a heavy animal compresses the soil. This reduces electrical resistance of the soil and increases the joules that can flow through the animal. 

This explains why heavy animals are more affected by electric fence and light animals less so. 

Weight (or the lack of it) explains in part why calves and lambs will seem to be less affected by a pulse than adult cows and ewes. 

Which species are most affected by an electric fence pulse?

In order from most to least: pigs, horses, cattle, canines (wet noses, bare pads) raccoons, sheep, goats, deer, geese, chickens and rabbits. 

This assumes a low-impedance energizer was used and adult animals are contacting the fence with their nose, beak or paw. 

Electric Fence Pulse

A pulse from an electric fence energizer lasts less than 3/10,000 of a second. The pulse's strength can reach up to 10,000 volts. That sounds extreme but static electricity is often as much as 25,000 volts.

What exactly is a fence energizer?

It is simply a box that takes in small amounts of electrical energy from an outside source (battery or 110v outlet).

The energizer pushes this energy from the outbound (positive, fence) terminal in very brief, high voltage and high amperage pulses, The ground terminal's (negative, earth) purpose is to absorb as much of the pulse energy as possible back into the energizer. 

An electric fence is the extension of these two terminals (fence and ground/earth).  

The inbound terminal is extended by driving metal rods (ground rods) into the soil and connecting them to the earth terminal with conductive wires to it. 

The outbound terminal is extended by attaching conductive wires to it. They are suspended above the soil and kept separate from the soil by insulators and/or nonconductive posts.