Question

The insulation resistance of a cable of length 100 km is 1 M$\Omega$. For a length of 10 km of the same cable, the insulation resistance will

• A. decrease by 20 times
• B. decrease by 5 times
• C. remain same
• D. increase by 10 times

Answer 1

The correct option is D increase by 10 times

Insulation resistance, $R=\frac{\rho }{2\pi l}ln\left(\frac{R}{r}\right)\Omega$

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

$R_2=1M\Omega \left(\frac{100}{10}\right)=10M\Omega$