Dissipation of Power by Resistors

[cwesto]

Homework Statement

Homework Equations

P=IV
I=V/R
P=(V/R)V
R=V²/R

The Attempt at a Solution

P_R1: 12²/12=12
P_R2: 144/18

I'm not sure what to do from here. Thanks for any input and help!

 

[LowlyPion]

Maybe start with how much current is passing through the resistors?

Your attempt incorrectly tried to use the total Voltage of the supply across the resistors singly. The question wants to know the power dissipated by each resistor.

Once you have the current then won't the power for any resistor be P = I²R ?

 

[cwesto]

I=V/R
R_total=12+18
I=12/30
P_R1=RI²
P_R1=12*$$\frac{2}{5}$$*$$\frac{2}{5}$$
P_R1=48/25

P_R2=$$\frac{72}{25}$$=2.88
Thanks!

 

[LowlyPion]

I=V/R
R_total=12+18
I=12/30
P_R1=RI²
P_R1=12*$$\frac{2}{5}$$*$$\frac{2}{5}$$
P_R1=48/25

P_R2=$$\frac{72}{25}$$=2.88
Thanks!

There you go. Good job.