What is constant flux linkage theorem?

Flux linkages of an inductive circuit can not abruptly change.

Proof:- This can be proved by the logic of contradiction. Let the flux linkages abruptly change. Then by Laws of Electromagnetic induction infinite voltage is to be induced Infinity is conceptual and not practical. Hence the flux linkages cannot abruptly change in any practical sense. Hence the theorem.

Some discussion and limitations of the theorem:- Although Infinity cannot be brought forth into the practical world, it is conceptualized in a limiting process by defining Impulse function. Thus if impulse functions can be considered, the constant flux linkage theorem can be violated.

How to justify the Word "Constant"?:- Considering a closed pure inductive circuit carrying a current I, it remains constant for ever, until infinity.