What equal length of an iron wire and a copper-nickel alloy wire, each of 2mm diameter connected parallel to give an equivalent resistance of $3Ω$ ?
(Given resistivities of iron and copper-nickel alloy wire are $12 μΩ cm$ and $51 μΩ cm$ respectively)

Question

What equal length of an iron wire and a copper-nickel alloy wire, each of 2mm diameter connected parallel to give an equivalent resistance of

3Ω

?
(Given resistivities of iron and copper-nickel alloy wire are

12 μΩ cm

and

51 μΩ cm

respectively)

Accepted Answer

Correct answer: B. (b) R_1R_2R_1+R_2=3 (12 10^-6 10^-2)l 4 (2 )^2 10^-6 (51 10^-6 10^-2)l 4 (2 )^2 10^-6 63 10^-6 10^-2 l 4 (2 )^2 10^-6 ⇒l=97m

$What equal length of an iron wire and a copper-nickel alloy wire, each of 2mm diameter connected parallel to give an equivalent resistance of 3Ω ? (Given resistivities of iron and copper-nickel alloy wire are 12 μΩ cm and 51 μΩ cm respectively)$