Pulse In Volts

 Your turn the key in the ignition, but nothing happens. No click, no idiots lights are illuminated, nothing. Chances are it's a dead battery. Of course, you get out, flip open the hood, and fiddle with some stuff. Maybe it will magically start working again, but you know better. If you're lucky, it's only the battery that's dead, and not a failed alternator that's caused the problem.

 As you return to the driver's seat, you run your hand along the front fender. The steel (or maybe plastic, depending on your car) feels strangely cold, lifeless. The spark of life is missing, and that's closer to the truth than is often realized.

 On most cars the frame and sometimes the sheetmetal itself acts as a wire, completing the circuit for the electronics. With your battery dead, billions of tiny little electrons have stopped travelling through the frame and sheetmetal. Like a terminal patient in the hospital, there is no pulse.

 Fortunately for us car nuts, all it takes is a new battery to bring our baby back to life.