A: Let me relate something that happened to a friend of mine, a
dentist by trade who likes to work on his sports car
occasionally. In preparation for some other work, he elected to
remove the battery from the car, using a box wrench to loosen
the battery clamps. The wrench made contact with his wedding
ring (he's lefthanded), and the ring in turn made contact with
the battery holddown. A massive short circuit welded his ring to
the holddown and to the wrench, which in turn was welded to the
positive terminal. Car batteries store an enormous amount of
energy, and they're optimized to deliver it in a very short
period of time. A shorted car battery can easily deliver several
hundred amps -- more than an arc-welding machine. Within a
second, my friend's wedding ring was almost red-hot, and only a
fast reaction with his other hand to break the connection by
hitting the wrench prevented it from remaining connected long
enough to melt. The ring had to be sawed off his finger at the
emergency room, and it was more t