Question

what is mechanism of glowing bulb

Answer 1

simple concept for this is that electrical energy converted into heat energy the filament of the bulb glow because the number of electrons moves from one end to another

Answer 2

The light bulb has a tungsten filament as the light emitting media and is specially manufactured by precision machines to give the correct cross sectional area. The tungsten filament is coiled to give a very high resistance and is encased in a glass envelope. This glass envelope or bulb is filled with a low pressure inert gas such as nitrogen or argon. When electricity passes through the coiled tungsten filament, it becomes hot and glows. The inert gas conducts the heat generated by the filament to the glass bulb from where the heat is radiated into the atmosphere.

 Instead of filling the tubes with inert gas, earlier bulbs used a vacuum to increase the life of the filament. The drawback of that arrangement was that the heat generated by the glowing filament would heat up the contact wires, often damaging the insulation and prematurely ending the life of the bulb.