Question

If the self inductance of 500 turns coil is 125 mH, then the self inductance of the similar coil of 800 mH

• A. 48.8 mH
• B. 200 mH
• C. 290 mH
• D. 320 mH

Answer 1

The correct option is D 320 mH

$L={\mu }_o{\mu }_r{N}^{2}Al$

For similar coil, $A,l$ will be same

So, $\frac{L_1}{L_2}=\frac{N_1^2}{N_2^2}$
$L_{800}=\frac{N_{800}^2}{N_{500}^2}\times L_{500}=\frac{125}{(500{)}^2}\times (800{)}^2=320mH$