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Potential Difference Across Resistors in Circuit

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Apr20-09, 10:56 PM
P: 2
Almost forgot to mention:
This is a DC Circuit!

In the diagram above, find the potential difference across the 3-ohm resistor.

a) 1.3 V
b) 3.0 V
c) 4.0 V
d) 5.0 V
e) 6.0 V

Relevant equations:
So far, I used: I = V/R to find current from the battery.
Then there's E = IR.
(Sorry, LaTeX doesn't like me.)

The attempt at a solution:
Using the first equation, I found that the current measures three Amperes.

I also tried using the second formula where I = 3 and R = 3, but that gave me 9 Volts, which isn't an answer.

Any help would be much appreciated!
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Apr20-09, 11:37 PM
HW Helper
P: 5,341
Welcome to PF.

Consider the equivalent resistance from the node above the 3Ω resistor to below.

If you determined the current was 3 a, then you must have determined that the Req was 2Ω.

In which case, your equivalent circuit looks like just two 2Ω resistors in series. That means then that the voltage at that node will be half of the battery supply.
Apr21-09, 12:05 AM
P: 2
Oh, duh! I totally forgot. Thank you!

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