Power transferred to resistance

[Tosh5457]

Homework Statement

Speaker Resistance = 10.4 Ohm
R = 8.20 Ohm
Maximum voltage of AC source = 15.0 V

What's the average power transferred to the speaker?

Homework Equations

P = $I^2R$
Imax = $I/2^0.5$

The Attempt at a Solution

I could the problem if there was only the speaker resistance. I don't understand how the other resistance comes into play or what it does in the circuit.

 

[tiny-tim]

Hi Tosh5457!

I could the problem if there was only the speaker resistance. I don't understand how the other resistance comes into play or what it does in the circuit.

The extra resistance reduces the current, I.

 

[gneill]

The other resistance, in series with the speaker resistance, form a voltage divider. Only a fraction of the supply voltage will appear across the speaker resistance.

You can determine the current through the series connected resistors, then using that current find the voltage developed across the speaker.

Keep in mind that you've been given the maximum voltage of the AC source. To find the average power you'll want the RMS values for voltage and current delivered to the speaker.