Question

A certain lightbulb has a tungsten filament with a resistance of 19.0 Ω when at 20.0°C and 140 Ω when hot. Assume the resistivity of tungsten varies linearly with temperature even over the large temperature range involved here. Find the temperature of the hot filament.

Answer 1

We know that

For tungsten

Now when

Also when, then the above equation gives

Or,

Or,

Or,

Or,

The temperature of the hot filament =