## Tuesday, July 30, 2013

### Ohm's Circle

There are four common variables in circuits.  P = Power, V = Voltage, I = Current, and R = Resistance.  Knowing any two of those you can find the other two.  To do this you must derive the right formula though.  I always remember that V = IR, and P = IV.  From that you can find these:
V = IR = sqrt(PR) = P / I
P = VI = V^2 / R = I^2 R
I = P/V = V/R = sqrt(P / R)
R = V/I = V^2 / P = P/I^2

I discovered something called Ohm's Circle which presents those formulas quite nicely.  However, I always just search for it and have never found a particularly well executed one.  Two of the top google image results have mistakes.  So, I decided to make my own version.  I derived the above formulas by hand to double check it was all correct.