The resistance of a bulb filament is 100 Ω at a temperature of 100°C. If its temperature coefficient of resistance be 0 .005/°C, its resistance will become 200 Ω at a temperature of

We know thatRt=R0[1+αΔT]Here 100=R0[1+0⋅005×100]………..(1)and 200=R0[1+0⋅005×T]…………….(2)where T is the temperature in °C at which the resistance becomes 200 ΩDividing eq. (2) by eq. [1), we get200100=1+0⋅005T1+0⋅005×100Solving, we get, T = 400°C