Wednesday, October 13, 2010

Power's relationship with Ohm's Law

Hey guys,

Today we're going to quickly review power's relationship with Ohm's Law (what we covered last time, V=I*R). Power is what your energy company charges you for, so you might want to pay attention!

We'll add on P = I * V

Where P = Watts (w) of power. One watt is equal to one Joule of energy expended in one second.

Well, what if we only have Voltage and Resistance? What if we only have Current and resistance? How can we solve for the power in a circuit? Ohm's Law (you'll see Ohm's Law a lot)

Since we have V = I*R, then we also have I = V/R (from dividing both sides by R)

Now substitute IR for V, or V/R for I (depending on what we're given to solve for P, and we have two more equations for power:

P = (V^2)/R
P = (I^2)*R

Now it's easy to solve for P if you're only given two of the variables in a circuit.

A great picture can be found at that neatly illustrates the relationship between power, voltage, current, and resistance. Check it out.


  1. Anything I can help you with? Just ask, sir/ma'am.

  2. love the physics tips

    btw, check out my new post on GTL Everyday :)

  3. haha, isn't that like, the first thing you learn during physics at school? :D

  4. Yeah I remember about this from back in the day

  5. Thanks, Tweek. If you have any questions, or requests, I'd be glad to help.

  6. I remember this stuff, lol. Following and looking forward to more.

  7. this reminds me of physics

    btw, check out my new post on Enhanced by MS Paint :)

  8. Reading some of this stuff makes me remember college...the part that sucked anyway.

    J/k, good stuff man, looking forward to more.

  9. cool, which college did you go to, LJ?