One henry of inductance is defined as: A. the amount of counter emf required to reduce a current to 1 A B. the amount of inductance required for generating 1 V of counter emf when the current changes at the rate of 1 A per second C. the amount of inductance required to change the frequency of a current by 1 Hz D. the number of turns of wire in an inductor multiplied by the amount of current flowing through it E. None of the above

The correct answer is: A. the amount of counter emf required to reduce a current to 1 A.

One henry is the amount of inductance required to produce an induced electromotive force (EMF) of 1 volt when the current through the inductor changes at a rate of 1 ampere per second.

Option B is incorrect because it is the amount of inductance required to generate 1 volt of counter EMF when the current changes at the rate of 1 ampere per second.

Option C is incorrect because it is the amount of inductance required to change the frequency of a current by 1 Hz.

Option D is incorrect because it is the number of turns of wire in an inductor multiplied by the amount of current flowing through it.

Option E is incorrect because it is not a valid option.