The Student Room Group

Maths

V=IR make R the subject
Reply 1
V/i = R
Original post by Skyehall
V=IR make R the subject

R =V/I (basic Ohms law).
Reply 3
What you're doing to get R on its own is dividing by I on both sides of the equals sign.

V=IR

V/I = IR/I .... and the 'I' s on the top and bottom of the fraction cancel

V/I = R

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The other thing people do is memorise the 'ohms law triangle'

To use that you put your thumb over the value you're interested in and what's left visible is the formula.

e.g 1 if you put your thumb over V all you can see is IR
V=IR

e.g 2 if you put your thumb over R all you can see is V over I
R=V/I

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