Question

The resistance of the bulb filament is 100 $\Omega$ at a temperature of 100${}^{\circ }$ C. If its temperature co-efficient of resistance be 0.005 per ${}^{\circ }$ C, its resistance will become 200 $\Omega$ at a temperature

• A. ${500}^{\circ }C$
• B. ${300}^{\circ }C$
• C. ${200}^{\circ }C$
• D. ${400}^{\circ }C$

Answer 1

The correct option is B

${300}^{\circ }C$

$\alpha =\frac{R_2-R_1}{R_1(t_2-t_1)}\Rightarrow 0.005=\frac{200-100}{100(t_2-100)}{t}_2={300}^{\circ }C$