- Thread starter rjmockster
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Don't forget that you can substitute from E=IR to P=IE and vice-versa. An example would be to substitute for E, P=I(IR) becomes P=I^2R.

I find that an Ohm's law equation can always be solved by remembering one rule:

I x R = E can be changed to

E / R = I or

E / I = R

It might be clearer to use numbers:

2 X 3 = 6 can be changed to

6 / 3 = 2 or

6 / 2 = 3

Given any two variables the third can always be deduced. I also think of this as being able to "unmultiply" something by dividing it in the opposite direction.

100w / 120v = .833333A and you need resistance

that's E / I = R or 120v / .833333A = 144ohms

[ May 09, 2003, 03:54 PM: Message edited by: physis ]

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Watts = volts x amperes, P = E x I. however, this is only where you have a purely resistive load or unity power factor, no inductive loads. Where inductive loads are supplied, watts = volts x amperes x power factor, P = E x I x PF.

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Re: Basic theory/formula's

DOCTOR WATTS pocket guide is pretty good too by Mark Shapiro.

DOCTOR WATTS pocket guide is pretty good too by Mark Shapiro.

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