Define self-inductance of a coil interms of (i) magnetic flux and (ii) induced emf.

Explanation

Self-induction. If I = 1A, then `L=NPhi_(B).` Self-inductance or simply inductance of a coil is defined as the flux linkage of the coil when 1 A curret flows throught it.
ii. When the current I changes with time, an emf is induced in it. Form Faraday's law of electromagnetic induction, this self-induced emf is given by
`epsilon(d(NPhi_(B)))/(dt)=-(d(Li))/(dt)" "...(1)`
`" "("using equation 1")`
`thereforeepsilon=-L(di)/(dt)`
`(or)L=(-epsilon)/(di//dt)`
ii. The negative sign in the above equation means that the self-induced emf always opposes the change in curret with respect to time. If `(di)/(dt)=As^(-1)," then "L=-epsilon.` Induction of a coil is also defined as the opposing emf induced in the coil when the rate of change of current through the coil is `1As^(-1).`