Question 308313
the electrical resistance of a wire directly with its 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.
:
let k = the constant of the variation
:
R = {{{(L*K)/r^2}}}
:
When R = 17 ohms
{{{(14*K)/1.3^2}}} = 17
{{{(14*K)/1.69}}} = 17
14K = 17 * 1.69
14k = 28.73
k = {{{28.73/14}}}
k = 2.052
:
Find R when L = 20, r = .8
R = {{{(20*2.052)/.8^2}}}
R = {{{41.043/.64}}}
R = 64.13 ohms