12 volts, two engineers and one ignorant teacher

Dear Tom and Ray: I am a junior in high school. In my physics class, the teacher claimed that you could be electrocuted by touching a car's battery terminals. I started laughing and said I know from experience that there is no way you could die from a car battery. She said I must have been very lucky. Everyone believes her just because she's the teacher. I even 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 is right?

Duell

Tom: You and your dad are right, Duell. 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) to do the job. 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. But the human body's resistance is much higher than that of metal.

Tom: The danger from car batteries is not so much electrocution as it is explosion. What you've just seen in action in the classroom is the difference between theoretical physics and applied physics. Your teacher knows all about electrical theory -- that's theoretical knowledge.

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 evening fell, we noticed 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 both have degrees from MIT and we'd both taken electrical engineering courses. But we sat there for an hour as it got darker and darker, unable to decide if we should attach the dangling wire, or if doing so would electrocute us and burn down the house.

Tom: As we sat there in the dark, debating the possible outcomes, some knucklehead who lived downstairs came bounding into the room and asked, "What are you guys doing sitting in the dark?" Before we could explain, he slid a chair over to the middle of the room, 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 exactly WHY she doesn't know diddly squat. And then you can go back to using your practical knowledge with the principal to try to get yourself out of detention for that one.