A while back I was doing an inspection and I needed my electric tester to determine if an exposed wire, beside a building, was energized or not. I had recently replaced my "tick" tester as we inspectors call them. I was not happy when I took it out, turned it on, and it immediately started beeping and lights were flashing when I was standing in the parking lot of the building I was inspecting.
I figured I had wasted my money on that one. Then I took out another one just like it. Imagine my surprise when it, too, started going wild. Now that was odd. I do not use the wimpy testers from home stores. I use testers that do not even beep until you are looking at 90 volts.
Suddenly the light in my head clicked on. I realized that I was inspecting near high tension lines. It makes sense, thinking about it, but I had never taken into account how intense the electromotive force is around such power lines.