The actual function of choke in tube light is to create a high voltage across the filament at starting and to limit the current when it normally glows. Read the full article carefully, then you understand the actual purpose of using choke in tube light.

First of all, let's know what is an electrical choke?

Choke is nothing but an inductor built with a coil of conductive wires. Generally, the choke used in tube light is built with conductive wires wound on a ferromagnetic material or core. It has the same properties as an inductor have. The voltage across the choke coil is proportional to the magnitude and the rate of change in current with respect to the time flowing through the choke coil. That means the voltage across a choke coil,

V= Ldi/dt, where L is the inductance

Now, let's see how a choke coil is connected with the tube light.

So, you can see the choke is connected in series with the tube light. That means whatever the tube light consumes current, it will flow through the choke.

At the starting time starter closed the contact, so the choke coil came across the full supply voltage. As the starting current is very high, the choke coil will produce a very high voltage across the filaments of the tube light. This high voltage will start the ionization of the gas inside the tube light. Once the gas inside the tube light is fully ionized it will glow and the current starts to flow through this ionized gas and two filaments. After glowing the tube light, the starter will open its contact, so no current will flow through the starter and the choke coil will come series with the tube light. So, as the current decreases the voltage across the choke also be decreased to a certain level. And the tube light will glow normally.

So, now you can understand the main function of choke in tube light is to produce a very high voltage at the starting that can ionize the gas. Also, we know that the inductive reactance(property of the inductor or choke coil that is nothing but the property to oppose the flow of current) depends upon the frequency. So when a surge voltage occurs, the choke coil also helps to meet protective the tube light by limiting the high current to flow.