Finding the unknown using a formula help
I need help using a formula to find the length of an electrical conductor.
(A) The cross sectional area of the conductor is 2.5mm2 which I have been told : 2.5 x 10^-6 (power of minus 6).
(R) The resistance is 0.86 (in ohms).
(P) The resistivity of the conductor is 17.24 nanohm metres which is : 17.24 x 10^-9 (power of minus 9).
(L) The length is unknown.
The formula was R: PL/A, now that length is unknown I believe the formula changes to L: RA/P?
So I came up with 0.86 x (2.5 x 10^-6) / 17.24 x 10^-9
Which gives me 1.25 (this ain't the right answer), did I go wrong in formula transposing or something?
Re: Finding the unknown using a formula help
You need to careful about the brackets (you need 17.24 x 10^-9 in one single bracket).
By using the brackets in the right place we get (from R) the answer to be:
since 10^-6 / 10^-9 = 10^3.