derive the expression average power associated with inductor?

Answer 1

well it depends whether u r talking about ac source or dc source i'll derive both the expressions:
when with dc:
E=Ldi/dt
Edq=Ldi/dt*dq
dW=Lidi
Integerating both sides
W=1/2Li^2
this expression per unit time gives the power
For Ac source:
P=EI*cos&
&=Phase Angle
&=90 for purely inductive circuit
so,
P=0 for AC source
Hope this helps u!