Question

2. The electrical resistance R of a wire varies inversely with the square of its diameter d. If a wire with a

diameter of 3 millimeters has a resistance of 0.4 ohm, find the resistance of a wire having the same

length and a diameter of 8 millimeters.

Answer 1

`0.225 \Omega =225 m\Omega`

Explanation:

We know (Ohm second law) that
`R= (k)/(d^2)` where k inlcudes the rest of the parameters (material, lenght). In our situation we have k=
`0.4\cdot9 \Omega mm^2`. The moment the diameter becomes 8mm R becomes

`R= {{0.4\cdot 9}\over{16}} \Omega = 0.225 \Omega`