# R circuit (pretty simple) need checked - full working - please

1. Jul 19, 2010

### pat666

R circuit (pretty simple) need checked - full working - please!!!

1. The problem statement, all variables and given/known data

see attachment

2. Relevant equations
P=IV
P_loss=I^2 R
V=IR

3. The attempt at a solution
ok
36=I^2*12

I_12Ω=√3 A
V=20.8V
That is the same for the 3 resistors in parallel (I hope)
so I18Ω=1.15A
I36Ω=0.577A
the sum of these will give me the current through the unknown resistor
Iunknown=3.46A
net voltage = 60
60=Vunknown + 20.8
Vunknown=39.2V
V=IR
R=11.3Ω

can someone please check this - wouldn't ask if I dint need it.

#### Attached Files:

• ###### resistors.png
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2. Jul 19, 2010

### rl.bhat

Re: R circuit (pretty simple) need checked - full working - please!!!

3. Jul 19, 2010

### pat666

4. Jul 19, 2010

### pat666

Re: R circuit (pretty simple) need checked - full working - please!!!

Sorry, I forgot the second half of the question,

P_loss=I^2 R
P=〖3.46〗^2*((1/12+1/18+1/36)^(-1)+11.3)
P_loss=207.6W
This seems big to me, could you please check that too.

5. Jul 20, 2010

### rl.bhat

Re: R circuit (pretty simple) need checked - full working - please!!!