Well, 3 questions actually. See below.

Please show me the working out and not just the answers.

Thanks in advance!

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- Sep 21st 2008, 10:48 PMJ4553Electrical Maths Questions
Well, 3 questions actually. See below.

Please show me the working out and not just the answers.

Thanks in advance! - Sep 22nd 2008, 03:32 AMCaptainBlack
For question 3 you are told that the resistance varies linearly with length and inversly as the square root of the diameter. That means there is a constant $\displaystyle k$ (other things being equal) such that:

$\displaystyle R=\frac{k l}{\sqrt{d}}$

You are given the resistance, 30.9 Ohms of a 850 mm length of 0.122 mm diameter wire so:

$\displaystyle k=\frac{30.9\sqrt{0.122}}{850}$

when resistance is given in Ohms and length and diameter in mm.

Now you know $\displaystyle k$ you can use the first equation to find the resistence of any wire of the same material.

RonL