Cell Phone Circuitry

Oct 12, 2002

RAY: This is the first automotive puzzler of the new puzzler season.

One day last summer, I got a frantic call at the shop from a woman, who explained that she was about to leave on a cross-country trip. She was worried because something very strange was going on. I said, "Why don't you just come on in." She seemed to be a little bit out of sorts.

Here's what was happening. When she plugged her cell phone into the cigarette lighter to recharge it, she noticed that the phone wasn't getting charged up. The little charging light didn't come on. Stranger still, the warning lights, including the battery and oil lights, lit up on her dashboard. She happened to be driving a Saab, but there are a lot of cars to which this could happen. She was worried that there was something wrong with her car, and that her cell phone wasn't going to get charged because of what was wrong.

TOM: And so when the car breaks down, which it was inevitably going to do, she wouldn't be able to make a call because her cell phone wasn't going to be charged. Of all the weird coincidences!

RAY: I took her cell phone and walked outside the garage. I made a call. I called the shop. One of the guys answered the phone, and I told him what was wrong with the car. A minute later, she drove away.

What did Ray tell the guy who answered the phone?


TOM: So that's the question.

RAY: And this is the correct answer. I was there and I witnessed it. Well, the first thing I had to do was to verify that her phone worked, because in order for my theory to be correct, the phone has to be working, because if the phone's dead, the theory doesn't work. So, in fact, by using her phone, I verified that her battery was not dead. Now, I need to give you a little lesson in electricity.

TOM: Go ahead, man.

RAY: When you plug something into your cigarette lighter like your hair dryer, or your portable yogurt maker, electrons that are in your car's battery stream out of that thing, go through the fuse, and go through the wires, and into the socket of your cigarette lighter. They operate whatever it is that you're operating. And everyone understands that principle.

TOM: Sure.

RAY: But when you plug in something that needs to be charged like the cell phone, something interesting is happening, because there are electrons in the cell phone. How do I know that? The battery isn't dead. And when you plug something in that needs to be charged, the reason it does get charged is there's a difference in electrical potential between the car's battery, which is 12 volts, and your cell phone, which is like eight, or nine, or 10 volts, or something like that. So, when you plug the cell phone into the cigarette lighter socket, electrons from your cell phone try to go into the wires in the opposite direction than those electrons from the battery are going.

RAY: So you get the scenario here?

TOM: I've got it, man.

RAY: Electrons are coming from your car's battery. The electrons from the cell phone are trying to escape, but something is wrong here, because things that aren't supposed to be working are working.

TOM: Yeah, I've got it. So your theory is that the electrons from the cell phone are going to light up the lights?

RAY: Exactly.

TOM: How's that happen?

RAY: When there were no electrons coming from the car's battery to the cigarette lighter, those nine volts of electrons in the cell phone, they are emboldened and they will travel wires that they were never intended to travel on and they will actually go to things and energize things like those lights on the dashboard that ain't supposed to be getting energized.

TOM: Wow, how bold. So lights will light up.

RAY: So what I told Manny when I called him on the phone was replace the fuse. She needed a fuse for the cigarette lighter. Anyway, do we have a winner?

TOM: The winner is Andy Gladish from Anacordes, Washington.

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