Question

A given wire has a resistance of 32 ohms. If its length is 872 m., how much length must be

cut-off from the wire in order to reduce its resistance to 13.4 ohms?

Answer 1

We know that

Resistance

$R=\frac{\rho l}{A}$

$R_1=\frac{\rho l_1}{A}$

Case (2)

$R_2=\frac{\rho l_2}{A}$

$\frac{R_1}{R_2}=\frac{l_1}{l_2}$

$l_2=\frac{R_2}{R_1}l_1$

$l_2=\frac{13.4}{32}\times872=365.15m$