A solenoid having area $A$ and length ' $l$ ' is filled with a material having relative permeability

Question

A solenoid having area $A$ and length ' $l$ ' is filled with a material having relative permeability 2 . The magnetic energy stored in the solenoid is\

Professor PC Thomas Classes · Answer

(b) : Given, Area $=A$, length $=l, \mu_{r}=2$\ $\frac{	ext { Energy }}{	ext { Volume }}=\frac{B^{2}}{2 \mu}$;\ $U=\frac{B^{2}}{2 \mu} 	imes$ Volume $=\frac{B^{2}}{2 	imes \mu_{r} \mu_{0}} 	imes A l$\ $U=\frac{B^{2} A l}{4 \mu_{0}}$\ $\left(\because \mu_{r}=2ight)$\