Two identical coils, each with self inductance L, are connected in series and kept very close. Turns wound in these coils have opposite sense of winding. Then resultant inductance of this connection is ......

Options

A. `L^2`
B. `2L`
C. `L/2`
D. zero

Answer

D

Explanation

Situation given in the statement is shown in the figure. Here when current passing through above series connection increases at a rate of `((dI)/(dt))` , self induced emf across series combination is,
`epsilon_(ac)=-epsilon + epsilon =0`
`therefore -L_(ac)(dI)/(dt)=0`
`therefore L_(ac)=0 (because (dI)/(dt) ne 0)`