Question

the electrical resistance of a wire varies directly with it's length and inversely with the square of its radius. if a wire with radius 1.3 millimeter and length 14 meters has a resistance of 17 ohms, what will be the resistance of a wire with radius 0.8 millimeter and length 20 meters. ______ohms

Answer 1

I tried this and my answer was smaller than 17 Ohms, meaning it was wrong! The solution has to be more than 17 as the length is longer, and radius is smaller. I will try it again (after lunch)

Answer 2

try 64 Ohms

Answer 3

I set up a proportion of:
17:8.28 :: x:31.25
x-64.16 Ohms

Answer 4

* change - to =

Answer 5

thanks a ton.

Answer 6

I did not convert mm to meters as both situations had similar units, I also did not try to find a proportional constant k. Should be close.