question_answer

 A short solenoid of radius a, number of turns per unit length \[{{n}_{1}}\] and length L is kept coaxially inside a very long solenoid of radius b, number of turns per unit length\[{{n}_{2}}\]. What is the mutual inductance of the system?

A)  \[{{\mu }_{0}}\pi {{b}^{2}}{{n}_{1}}{{n}_{2}}L\]

B)  \[{{\mu }_{0}}\pi {{a}^{2}}{{n}_{1}}{{n}_{2}}{{L}^{2}}\]

C)  \[{{\mu }_{0}}\pi {{a}^{2}}{{n}_{1}}{{n}_{2}}L\]       

D)  \[{{\mu }_{0}}\pi {{b}^{2}}{{n}_{1}}{{n}_{2}}{{L}^{2}}\]