Calculating Power Dissipation in a Simple Circuit

[BuBbLeS01]

Homework Statement

How much power is dissipated by R1? (R1=8 Ω, R2=17 Ω, V=6 V.)

Sorry the picture is so big!

Homework Equations

The Attempt at a Solution

P = E^2/R = 8^2/6 = 10.67W what am I doing wrong?

 

[BuBbLeS01]

Do I have to add the resistors??

 

[Mthees08]

No P=IV so the change in power is the dissipation of power so delta P=IV-IV
so use v=IR and get P=I^2R -I^2R for the points after and at (before) the resistor, also remember always final-initial

 

[BuBbLeS01]

So I would do...
I = E/Req = 6/25
P = 0.24^2 * 8 - 0.24^2 * 17 = -0.5184
Negative? Why would it be negative?

 

[BuBbLeS01]

Can someone explain this...

No P=IV so the change in power is the dissipation of power so delta P=IV-IV
so use v=IR and get P=I^2R -I^2R for the points after and at (before) the resistor, also remember always final-initial

I don't understand what Vi and Vf are?

 

[BuBbLeS01]

so i need to multiply the voltage drop across the resistors by the current. but how do i calculate the voltage drop?

 

[BuBbLeS01]

solved...