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) ${300}^{\circ }C$

Given,

Resistance of the filament is 100 ohm at ${100}^{0}C$

Temperature coefficient = 0.005 per ${}^{\circ }$ C

We know,

$R=R_0(1+\alpha (T_2-T_1))$

Putting all the values

$200=100(1+0.005(T_2-100))$

After solving

$T_2={300}^{0}C$

Hence temperature is ${300}^{0}C$