http://session.masteringphysics.com/problemAsset/1169458/2/jfk.Figure.23.P50.jpg

The 10 Ω resistor in the figure is dissipating 40 W of power. (Figure 1) How much power is the 20Ω resistor dissipating?

Question

http://session.masteringphysics.com/problemAsset/1169458/2/jfk.Figure.23.P50.jpg

The 10 Ω resistor in the figure is dissipating 40 W of power. (Figure 1) How much power is the 20Ω resistor dissipating?

anonymous · Answer

P = V^2/R

So, since it's parallel the voltage is the same.

V^2 = P * R
       = 40W * 10Ω
       = 400

Power in 20Ω = V^2/R
                      = 400/20
                      = 20W