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Derivations of Formulas

So what is a derivation? Well, when selecting a formula to find a missing value in an electrical problem, the unknown value needs to be by itself on one side of the equation and the known values need to be on the other side of the equation. Finding a formula in this format might not be easy. So here's what can be done.

Say you have the formula E = I R well, you in this problem have no access to all the Ohms Watts formulas. So you need to find R because you have I and E. To get R by itself, you are allowed by the rules of algebra to do what ever you want to both sides of the equation to keep it balanced.

So you can divide both sides of the equation by I. That will yield R = E / I. You then can go ahead and solve for R with the values you know of I and E. Of course if you have the formulas on a sheet of paper in front of you, none of this is necessary. You can just look up a formula you need from the list.

So keep in mind that if you ever do need to derive a formula, start with a formula you have. Then you can:

    add the same amount to each side.
    subtract the same amount from each side.
    multiply each side by the same number.
    divide each side by the same number.
    square each side.
    take the square root of each side.

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