An Inductor is basically just a wound conductor to form a coil. Inductance is a property of conductor due to which an electromotive force is induced by varying current flowing through the conductor. EMF gets induced due to varying current in itself (self-inductance) and also in conductors that are in close proximity (mutual inductance).

So, when an alternating current flows through an inductor, EMF gets induced in it due to self-inductance. But, according to Lenz’s law, direction of the induced EMF must be so that it opposes the cause of its generation, i.e. change in current.. So, the self-induced EMF opposes the AC current in an inductor.

This can also be understood from the Inductive reactance formula.

Inductive reactance X = 2 * pi * f * L

Now, by above equation, reactance for DC current will be 0, as frequency of dc current is 0. As the frequency increases, the reactance also increases proportionally. Thus, inductor opposes the AC current, and opposition to AC current increases as the frequency increases.

In case of a tube light, the choke is basically an inductor with iron core. An iron core inductor offers more inductance than air core. An inductor has a property to throw back the energy stored in it, when the voltage applied to it is lowered or turned off. In a tube light, a choke is connected in series with the parallel combination of a starter and fluorescent tube. The starter is made up of discharge bulb with two electrodes. When we apply voltage, the choke starts energizing as the electrodes in starter are short. Due to working principle of the starter, it turns off in few moments. When the starter turns off, the choke circuit opens, and it tends to throw out its energy in addition with supply voltage through the flueroscent tube.