Question

Two coils connected in parallel having resistances 300 $\Omega$ and 200 $\Omega at{20}^{0}C$ and temperature coefficient of resistivity 0.001 $K^{-1}$ and 0.006 $K^{-1}$ respectively.The effective temperature coefficient of the combination is

• A. 0.007 $K^{-1}$
• B. $0.004K^{-1}$
• C. $0.002K^{-1}$
• D. $0.003K^{-1}$

Answer 1

Answer: (B)

$0.004K^{-1}$

$\alpha =\frac{R_2{\alpha }_1+R_1{\alpha }_2}{R_1+R_2}=\frac{200\times 0.001+300\times 0.006}{200+300}=\frac{2}{500}=0.004K^{-1}$.