# Speaker and Battery

1. Apr 5, 2007

1. The problem statement, all variables and given/known data

Hey guys........I'm helping my girlfriend again, in her intro physics. We never went over this stuff, in my more advance physics. Her question is this:

What would a speaker do the instant a low-voltage battery is connected to it?

2. Relevant equations

3. The attempt at a solution

I am not sure......I'm guessing that it would make a humming noise....but that is just a guess. She can't find it in her book, and I'm not there to look at it. Any way of explaining it to me, so I can try to teach it to her(she needs to actually know "why"....not just the answer).

Thanks!

PS....she just typed to me, and she thinks that it just "won't work"......so, if that is the answer....haha.....just say. ***Edit....Typed more to me.....She thinks it won't work, due to it being a low power source, and a DC current. This makes sense to me......but then I think about car speakers, but I think they are ran through a converter/booster.

Last edited: Apr 5, 2007
2. Apr 5, 2007

### chroot

Staff Emeritus
The voice coil is an inductor, which is a short circuit to DC. The speaker cone would move a tiny bit the instant the battery is connected, perhaps making an audible popping sound, and then would stop moving when the magnetic field is fully established in the voice coil. The battery would then simply discharge itself through the voice coil, perhaps heating up and destroying it in the process.

- Warren

3. Apr 5, 2007

I understand what you are saying....is this the right answer for physics 101(if you understand what I'm saying)??

4. Apr 5, 2007

### chroot

Staff Emeritus
It's the right answer for Physics 101, Physics 202 and the electrical engineering industry. Indeed the universe itself approves of my answer whole-heartedly. (I asked.)

- Warren

5. Apr 5, 2007