A resistance of 2Ω is to be made from a copper wire (specific resistance $1.7 × 10^{-8}Ω m$) using a wire of length 50 cm. The radius of the wire is
Answer & explanation
Correct answer: option 2
$R = \frac{\rho l}{A}$
$ A = \frac{\rho l}{R} = \frac{1.7\times 10^{-8}\times 0.5}{2} = \pi r^2$
$\Rightarrow r = 0.0367mm$