Electrical Engineers Learn The Hard Way
RAY: This puzzler is from Gary from Santa Clara, California. It's kind of an automotive puzzler.
"As a shade tree mechanic, I've read many times that when removing a car's battery or doing electrical work, one is supposed to disconnect the negative terminal first, and only then, the positive terminal. Installation, as so many instructions say, is the reverse of that procedure.
"Now, as an electrical engineer, I scoffed at these instructions, because I knew that opening a circuit at any point was equivalent to opening it anywhere else. I just disconnected whatever terminal was handy. One day, I was helping a friend change the battery in his garden tractor. He happened to be an electrician, and he knew as well as I did that it didn't matter which terminal was removed first.
"But, as we learned that hard way that day, this isn't true. It does matter which is removed and replaced first.
"Why is that?"
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[ Car Talk Puzzler ]