Question

If the number of turns per unit length of a coil of a solenoid is tripled, then the self – inductance of the solenoid will becomes

• A. Nine times
• B. Remain constant
• C. Halved
• D. Doubled

Answer 1

The correct option is A Nine times

$L\propto n^2$
$\frac{L_1}{L}={\left[\frac{n_1}{n}\right]}^2={\left[\frac{3n}{n}\right]}^2=9$
$L_1=9L$