Fluorescent lights are among the most popular lighting system used worldwide. Fluorescent tubes/lamps are filled with mercury vapor. They use electric charge to excite mercury atoms in order to produce ultra violet light. A glow starter or commonly known as starter is used in the tube light circuit to provide an initial current to filaments of the tube light. To understand the purpose exactly why a starter is used in the tube light circuit, let’s look into its circuit.
When the switch is pressed current cannot pass through the tube initially because the gas inside it is not ionized and hence the tube light circuit behaves as open circuit. Once the gas is ionized, it will provide a conduction path for the current to flow. In order to ionize the gas, an initial high current is required for a short period across the filaments of the main tube. That is what a starter does. A starter initially provides a path to complete the circuit and once tube light starts the current flows through the ionized gas in the main tube.
The above image shows a typical starter connected in parallel with the florescent lamp.
It is a cylindrical can with two terminals, as shown in the above pictures. These two terminals are used to electrically connect the starter with the rest of the circuit.