# [Circuits] Calculating the power absorbed by a resistor

1. Jan 20, 2014

### ainster31

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

2. Relevant equations

3. The attempt at a solution

Attached to this post.

I have calculated the power absorbed for the 6S and 5S resistors but not the 3S resistor.

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2. Jan 20, 2014

### Staff: Mentor

Your values look okay for the 6S and 5S resistors. Why didn't you calculate the power absorbed by the 3S resistor?

3. Jan 20, 2014

### ainster31

Here is my attempt for the 3S resistor:

$$R=\frac { V }{ I } \\ \frac { 1 }{ 3 } =\frac { V }{ 6 } \\ V=2\quad V\\ \\ P=VI\\ P=2\cdot 16\\ P=32\quad W$$

4. Jan 20, 2014

### Staff: Mentor

Where did you get 16 A from for your P = VI calculation? You used I = 6 A in the second line.

Note that while power is indeed given by P = VI, for a resistor it's also given by V2/R and I2R, so you can avoid some steps if you already have either V or I.

5. Jan 20, 2014

### ainster31

So P=12W?

6. Jan 20, 2014

### Staff: Mentor

Is that a guess or a conclusion?

7. Jan 20, 2014

### ainster31

Conclusion.

I used 16 A by accident. Not sure where I got the 1 from.

8. Jan 20, 2014

### Staff: Mentor

Okay, so it looks like you're done

9. Jan 23, 2014

### HugeLaser

You got right.