**Date:** Mon Mar 9 20:18:27 2009

**Author:** Anthony Lapinski

**Subject:** stereo speakers

**Post:**

I was discussing Ohm's law today, and a few students were asking about

stereo speakers and their resistance. Textbooks do few problems involving

speakers. From my understanding, a typical speaker is 8 ohms. This will

get a certain amount of current and voltage, providing a power (P = IV) to

the speakers. If one replaces the speaker with one that has a lower

resistance, does this mean that the current (and power) will increase for

a given voltage? Or is it that for a given power (volume), the current

will increase while the voltage will decrease (since R is now less)? And

the implication is that when the volume is turned up (P increases), an

amplifier must have a better power rating to supply the sound if the

speaker resistance is lower.

Is this correct? Can anyone provide some "basic" physics information about

speakers, amplifiers, and Ohm's law?