Answer:
1275.61° C
Step-by-step explanation:
The resistance of a conductor varies as a function of temperature and it is given as follows
![R= R_o[1+\alpha(T-T_0)]](https://img.qammunity.org/2020/formulas/physics/college/lummk7kl5c8y6an5l98la5ju25hel48u40.png)
R_0 is the resistance at temperature T_0, R is the resistance at T and α is the coefficient of temperature of resistance
α= 0.0045/°C
R_0 = 20.3Ω T_0 = 20°C and R= 135Ω
![135= 20.3[1+0.0045(T-20)]](https://img.qammunity.org/2020/formulas/physics/college/texhwrlbx8shf0c1j3h9q5dbyk88xz67yo.png)
T= 1275.61° C
Therefore the temperature of the hot filament = 1275.61° C