Dear Tom and Ray: I am a junior in high school. In my physics class, the teacher claimed you could be electrocuted by touching a car’s battery terminals. I laughed and said I know from experience there is no way you could die from a car battery. She said I must have been lucky. It makes me mad, because everyone believes her because she’s the teacher. I asked my dad, and he said maybe it would make your heart flutter if you touched both terminals to your chest while pouring water over yourself. Who’s right?

– Duell

Tom: You and your dad are right. While a car battery has enough amperage (electrical power) to kill you, it doesn’t have enough voltage (electrical force – to push the electrons through your body). Your body is just not conductive enough to be fried by 12 volts.

Ray: If you were made of metal, 12 volts would crisp your circuits.

Tom: The danger from car batteries is not so much electrocution as it is explosion. If you touch both terminals with a metal wrench, for instance, you can create a spark that can ignite hydrogen gas in the battery. That can send pieces of battery and acid flying.

Ray: Which is why my brother’s face looks like it does.

Tom: What you saw in class is the difference between theoretical physics and applied physics. Your teacher knows all about electrical theory.

Ray: Your father, on the other hand, has stripped off his shirt, laid his bare chest on a pair of battery terminals, and turned the hose on himself. That’s applied physics – and probably as good a reason as any to avoid alcoholic beverages and college fraternities.

Tom: My brother and I had a similar demonstration years ago. He had just rented his first apartment, and I was over there helping him slap some paint on the walls. As the day wore on, it got dark. But the only light in the room was a bulb on the ceiling that had one of its wires detached.

Ray: Now, my brother and I have degrees from MIT. And we’d both taken electrical engineering courses. But we sat there for an hour as it got darker, unable to decide if we should attach the wire, or if that would electrocute us and burn down the house.

Tom: So some knucklehead who lived downstairs came in and asked, “What are you guys doing sitting in the dark?” He slid a chair over, slapped the wire back on with his fingers, and the light bulb came on.

Ray: Now, our point is not that education is overrated. Our point is that, if you’re going to be an engineer, it’s good to have both theoretical and practical experience.

Tom: You’ve got some practical knowledge already, Duell. Now you need to learn the theoretical so you can explain to your teacher why she was wrong. And then you can go back to using your practical knowledge with the principal to try to get out of detention.

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