Question

Another Circuit problem. (See attachment)

Answer 1

For some reason, I keep crashing every time I come onto this site. -_-

Answer 2

Okay, I have absolutely no idea how to figure this out because my teacher didn't teach it to us (that is "power dissipation" or whatever). Upon internet research, I found that P = RI^2. Not sure?

@theEric

Answer 3

I'm going to look at the problem in a moment, but
\(P=VI=I^2R=\dfrac {V^2}{R}\)

Answer 4

So, which formula do you think would be most appropriate?

Answer 5

Easiest, I mean.

Answer 6

Well, we already have voltage and resistance, right?

Answer 7

I think that one will be easiest, too!

So, you will use \(P=\dfrac{V^2}R\).

Answer 8

So, do you have a plan of action on finding the voltage across \(R\)?

It's always good to start with a plan of action.

Answer 9

Well.. I thought we would just plug in the values for v and r (or 18 and 15), but I don't think that's how it goes either.

Answer 10

We start by finding the total resistance?

Answer 11

And the formula is the voltage across and resistance of the resistor in question.

That's a start! Now, is \(15\rm\ V\) the voltage across that resistor?
That's a good start, too, finding the total resistance.

Answer 12

I will give you a hint, because I'm not sure if you've seen this or not. The voltage across \(R_3\) is the voltage across that parallel pair, there.

Answer 13

So would it be a lot like the other problem we did? 1/(13 + 18) ?

Answer 14

Resistance of the two parallel resistors would be .13? Sorry if it's not right lol, I am terrible at physics.

Answer 15

Haha, the circuits involve a lot of memorization. Organizing it would help. I want to go into electronics, but it took me a while to get the basics sorted out. I still won't know a lot until I take more classes.

Do you know how to find the "equivalence resistance" of a bunch of parallel resistors?

Answer 16

Your formula is close!

Answer 17

Okay, I am going to attempt to tell you how I got the answer lol. I got 2. Give me one second to type everything out.

Answer 18

\(\Large\dfrac1{\frac1{13}+\frac1{18}}\)

Answer 19

Dang, right when I typed everything out I accidentally clicked on something. Fudge! Lol.

1/(1/13 + 1/18) = 7.55

7.55 + 8.5 + 3.2 = 19.25

15/19.25 = 0.78

7.55 * 0.78 = 5.88

5.88^2 = 34.57
34.57/18 = 1.9 or 2 W

Answer 20

I would go with \(1.9\rm\ W\)! I agree! :)

Answer 21

Thank you!! I think the thing that threw me off the most was 1 / (1/13) + 1/18). I didn't use 1 as the numerator in the other problem as well, which was why my answer was way off. But I appreciate your help! :D

Answer 22

Okay! You're welcome! :)