Each channel of a stereo receiver is capable of an average power output of 100 W into an $8$-$\Omega$ loudspeaker (see Fig. 18–14). What are the rms voltage and the rms current fed to the speaker

VIDEO TRANSCRIPT

This is Giancoli Answers with Mr. Dychko. Average power dissipated is root mean square voltage, squared divided by resistance. So we can solve for V rms by multiplying both sides by R and then taking the square root of both sides. So V rms is square root of the average power times the resistance. So thats square root of 100 watts times eight ohms and that's 30 volts approximately and to find the R.M.S current, the average power is I rms current squared times resistance and we divide both sides by R and switch the sides around and take the square root of both sides and we get R.M.S current is the square root of power over resistance. That's 100 wants divided by eight times, square rooted. That gives about four amps. And then if we have one watt of power the formulas are the same and we have square root of one watt times eight ohms which is three volts R.M.S and the R.M.S current is square root of one watt divided by eight ohms which is 0.4 Amps.