1) Two resistance equal at 0° c with a temperature coefficient of resistance $\alpha_{1}$ and $\alpha_{2}$ joined in the series act as a single resistance coefficient in a circuit. The temperature coefficient of their single resistance will be A) $\alpha_{1}+\alpha_{2}$ B) $\frac{\alpha_{1}\alpha_{2}}{\alpha_{1}+\alpha_{2}}$ C) $\frac{\alpha_{1}-\alpha_{2}}{2}$ D) $\frac{\alpha_{1}+\alpha_{2}}{2}$ Answer: Option DExplanation:$R_{1}=R_{0}(1+\alpha_{1} t)+R_{0}(1+\alpha_{2} t)=2R_{0}\left(1+\frac{\alpha_{1}+\alpha_{2}}{2}t\right)$ Comparing R= R0 (1+$\alpha$ t) $\alpha$ =$\frac{\alpha_{1}+\alpha_{2}}{2}$
