Question

The resistance of a coi is $4.2\Omega$ at ${100}^{\circ }C$ and the temperature coefficient of resistance of its material is $0.004{/}^{\circ }C$ . Its resistance at $0^{\circ }C$

• A. $6.5\Omega$
• B. $3\Omega$
• C. $5\Omega$
• D. $4\Omega$

Answer 1

The correct option is B $3\Omega$

$\begin{array}{c}R=R_0\left(1+\alpha \Delta T\right)\\ 4.2=R_0\left(1+0.004\times 100\right)\\ 4.2=R_0\left(1+0.4\right)\\ R_0=\frac{4.2}{1.4}=3\Omega \end{array}$

Hence,

option $\left(B\right)$ is correct answer.