Find the resistance of `240 V - 200` watt electric bulb when glowing. If this resistance is `10` times the resistance at `0^(@)C` and the temperature of the glowing filament is `2000^(@)C`, then find the temperature coefficient of resistance of the filament.

Options

A. `28.8Omega,(4.5xx10^(-3))/(.^(@)C)`
B. `14.4Omega,(4.5xx10^(-3))/(.^(@)C)`
C. `28.8Omega,(3.5xx10^(-3))^(^(@)C)`
D. `14.4Omega,(3.5xx10^(-3))^(.^(@)C)`

Answer

A

Explanation

Resistance of the hot bulb `R_(2)=(V^(2))/(P)=(240xx240)/(200)`
Resistance of the bulb at room temperature
`R_(1)=(R_(2))/(10)=(288)/(100)`
`alpha=(R_(2)-R_(1))/(R_(1)t)`