Question

Why the filament of bulb glows ?

• A. Excess of electricity passing through bulb filament, hence it glows
• B. Current passes through the filament, it gets heated up and become red hot, hence glows
• C. Current passing through filament cools it down, hence it glows
• D. None of these

Answer 1

Answer: (B)

Current passes through the filament, it gets heated up and become red hot, hence glows

A filament has a lot of resistance to electricity. Therefore as a result of this, the filament heats up and become red hot and starts glowing, converting electrical energy to light energy. This is because of the Joule-effect, which means that resistances heat up when the electrical current runs through them.