Discussion Forum



1)

The magnetic field (B)  inside a long solenoid  having n turns per unit length and carrying current l when the iron core is kept  in it is ($\mu _{0}=$ permeability  of vacuum, $\chi$= magnetic susceptibility)


A) $\mu_{0}nl(1-\chi)$

B) $\mu_{0}nl\chi$

C) $\mu_{0}nl^{2}(1+\chi)$

D) $\mu_{0}nl^{}(1+\chi)$

Answer:

Option D

Explanation:

According to question, charge in magnetic field due to insertion of iron core is given by

 B'=$\mu$ B

=  $\mu_{0}(1+\chi)B  [\because\mu=\mu_{0}(1+\chi)]$

where, B= magnetic field  in air 

 $\mu _{0}$= permeability of vacuum

 $\chi$= magnetic susceptibility

As we know magnetic field inside the solenoid is given by $ B= \mu_{0} nl$

So, B'= $\mu _{0}(1+\chi)$ nl