Question

In lighting insulation using filament lamps, voltage drop of 1% results in:
1. No loss of light
2. 3.5% loss in the light output
3. 1.5% loss in the light output
4. 15% loss in the light output

Answer 1

Correct Answer - Option 2 : 3.5% loss in the light output

The output of the light of a filament lamp is depends on the temperature of the filament.

At very high temperature, the vaporization of filament decreases the coil’s diameter so that resistance of the filament increases. Hence it draws less current from the supply, so the temperature of the filament and the light output of the bulb decrease.

In lighting insulation using filament lamps, voltage drop of 1% results in 3.5% loss in the light output.