Calculating current used by individual resistor?

I just recently finished a test on Physics, and when receiving my scores back I missed a question. Here's what it was if I can remember it correctly:

Three resistors (10.0, 15.0, and 6.00 ohms) are parallel and the circuit is powered by 12.0V. How much current (in amps) is the 6.00 ohm resistor using?

So:

|-----------------|----------------|---------------|
|                 |                |               |
--(12.0 V)        <(10.0 ohms)     <(15.0 ohms)    <(6.00 ohms)
-                 >                >               >
|                 |                |               |
|                 |                |               |
----------------------------------------------------


So, I assumed that since you can combine parallel resistors into one equivilent resistor, they use the same amount of current.

So I just found the current used (4.00 A), and assumed that the 6.00 ohms resistor used the same current. The teacher, however, stated that the correct answer was 2.00 A.

Am I right or wrong? Why?

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 I'm tagging this homework because it's a question of educational value (even though I recognize it's not an actual homework question). – David Zaslavsky♦ May 12 '11 at 17:54 Thank you David, I was debating whether to use it or not. :) – Ramp May 12 '11 at 17:56 A resistor does not "use" current! The current flows through the resistor. – Georg May 13 '11 at 2:21

Think about this: the current through a certain circuit element represents the amount of charge that flows through that element per second. In a case like this, it's electrons that carry the current, so the amount of current is related to the amount of electrons that flow per second.

Now, you found that a total of $4\ \mathrm{A}$ of current flow through the circuit. Suppose that corresponds to a total of $N$ electrons per second. Are all $N$ of those electrons going to go through the $6\ \Omega$ resistor?

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 Okay, I see what you mean. Then how would I calculate that? I just feel rather cheated or something because he never taught us how to do that. I guess you just make a ratio of the resistors and then take that portion of the total current? How would that come out to 2.00 A, then? – Ramp May 12 '11 at 17:51 @Ramp: do you know what property of parallel resistors has to be the same? (It's not the current) – David Zaslavsky♦ May 12 '11 at 17:53 @David: Are you talking about voltage? – Ramp May 12 '11 at 17:57 @Ramp: yep, that's the one ;-) Knowing that the voltage is the same across parallel resistors (which I would hope you were taught) is the fact you need to figure out how much current flows in each. – David Zaslavsky♦ May 12 '11 at 19:42 I doubt that going down to electrons/sec helps a lot for someone who is thought to apply Kirchoff, not more. – Georg May 13 '11 at 2:23

Only if the resistors are the same, they carry the same amount of current. Otherwise, the current is distributed according to the ratio of their resistances.

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