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Ohm's law power formula question

Ok, using ohm's law, in a DC circuit, we can say that:

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

But what if you have a one ohm resistor?

Example, one ohm resistor with 0.25A going through. V=I*R, so V= 0.25 x 1 = 0.25A

using the formula, power = V*I, you get 0.25W but using the other formula (V^2)/R, you get 0.0625W

0.0625 != 0.25W

Let's try 4 ohm resistor with 0.5A flowing through: V=I*R, V= 0.5 x 4 = 2V P= V*I = 2 x 0.5 = 1W P=(V^2)/R = (2^2)/4 =1W P= (I^2) * R = (0.5 x 0.5) * 4 =1W

Why isn't it working and what did I not do right?

Reply to
ITSME.ULTIMATE
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First example V = .25, I = .25 so V x I = .25 x.25 = .0625

Reply to
Dan H

Thats .25V

V does not equal 1 ! P=IE P=.25^2=.0625W

You just messed up your variables......I assume you are a student and all I can say is you REALLY need to know these two formula's inside and out. They will serve you well into the future....good luck....Ross

Reply to
Ross Mac 

--
     E = IR = 0.25A * 1R = 0.25V

_not_ 0.25A
Reply to
John Fields

0.25 Volts actually !

No P=V * I = 0.25 * 0.25 = 0.0625W

Yes - correct. Your first instance was wrong.

No P=V * I = 2V * 0.5A = 1W

You've gone mad.

Graham

Reply to
Pooh Bear

--- No, he hasn't. He just made a simple error in the first part of his post which he couldn't reconcile.

This is sci.electronics.basics, where anyone should be able to ask any questions they might want to, no matter how stupid those question might seem to be and, with the answers to those questions in hand, walk away a little more informed than they were when they first got here without feeling any guilt for their earlier ignorance.

Your pejorative comments seem to be designed to denigrate the querant(s) into believing that your judgement of their submissions matters because they're stupider than you are.

They may or not be true, but if they're asking for help and you smugly deny it, then what's to be said in your favor?

-- John Fields Professional Circuit Designer

Reply to
John Fields

Well, actually he got 'confused' about the value of I.

Ergo my response ! ;-)

Graham

Reply to
Pooh Bear

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