Maybe it was at a cocktail party or at your son’s baseball game or back in high school, but I bet at least once in your life you had someone tell you this piece of advice. They probably didn’t use the terms shock hazard, step potential, or touch potential, but this is probably how it went.
“Did you know…” started the guy who seems to know everything, “that if you ever crash your car into a telephone pole, and a power line falls, the only way to get away from the car is to jump with both feet together and not fall over?”
Have you heard that one? Yeah me too. A few times. The truth is that he’s on to something and it’s a very fundamental concept behind getting a shock and what you need to know to avoid getting one.
What is a shock anyway?
A shock is the flow of charged electrons through your body, usually described as current. The more current that flows the more damage it does to your health and the greater the chances of stopping your heart.
What makes the electrons flow?
The natural tendency of electrons is to flow from a greater potential (or voltage) to a lesser potential until things level off. Here is a fun analogy using water in the place of charged electrons.
Picture two identical water tanks that are connected at the bottom by a pipe and a valve in the middle of the pipe. The tank on the left is full to the top with water and the tank on the right is empty. If I opened the valve what is going to happen? Well… the water from the left tank will flow through the pipe and fill the right tank until the level in the two tanks is the same.
Electrons want to do the same thing. When you get a shock it’s because you have touched two things with different levels of charged electrons, the electrons want to flow through your body until they level off.
So how does this tie into the story above?
Good question. First, let’s look at why it’s recommended to have both feet together.
Picture the power line which has fallen on the ground and let’s assume that it is still energized. There will be a high concentration of charged electrons right at the point where the line is touching the ground. Normally the ground is at zero potential. As you move over the ground further and further away from the point of contact the potential is getting less and less.
If your feet are not together and you took a giant step your body is now touching two points with a difference in potential. The charged electrons are going to want to flow through your body and level off that difference in potential.
Now let’s look at why you might want to jump from the car.
This time imagine that the power line fell directly on the car itself. Because of the insulation offered by the rubber tires on the car let’s assume that the ground remains at a zero potential. The car, on the other hand, will be at a very high potential.
If you were to step down to the ground with one hand still on the car, then you’ve just done it again. You’ve created the path for electrons to flow from one potential to another. You are the pipe connecting the two water tanks.
How can I apply this information?
Now I understand that the probability of crashing your car into a telephone pole and having live power lines fall to the ground is small but I think it offers something you can visualize. The thing is that this concept can happen in any industrial facility and even in your home.
Depending on how your electrical system is set up you could have a heater, a piece of switchgear, or a toaster for sake of argument where one electrical conductor has malfunctioned and is touching the frame of the equipment. This would bring the potential of the frame from zero to a very high level. As soon as you come in contact with the frame you’re now creating that path for the electrons to flow.
The best way to protect yourself from this is not to touch electrical equipment with your bare hands, and if you ever get a tingle from a toaster or other home appliance immediately take it out of service and have it properly disposed of.
I hope you found this article useful and if you did please share it using the social media buttons at the bottom of the post! Also if you would like some help with your electrical safety program, feel free to contact me anytime.