69.

It may help you to isolate the unknown quantity in the formula

if you will compare the process with another process you

already understand.

Remember the "magic circle" for Ohm's law?

What is the formula

if you wish to solve for E?

69a. E = I X R

b.

What is the formula if you wish to solve for R?

_____________________

69b.

70.

Now, isolate I, as you did E and R in the preceding steps.

_____________________

70.

71.

After the unknown quantity has been isolated to the left of the

equal sign, substitute known values for the symbols to the

right of the equal sign and solve mathematically.

Solve for R, when e = 100 and I = .2

Answer here. ________________

Solve for E when R = 250 and I = 4

Answer here. ________________

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