Question

Identify the temperature at which the resistance of copper would be double of its resistance at ^oC. Given α (temperature coefficient of resistivity) for copper=3.9 x 10^-3 ^oC^-1.

(a) 125^oC

(b) 256^oC

(c) 1080^oC

(d) 273^oC

The question was posed to me in an international level competition.

This is a very interesting question from Current Electricity topic in portion Current Electricity of Physics – Class 12

Answer 1

The correct choice is (b) 256^oC

Easy explanation: α=\(\frac {(R_2-R_1)}{R_2(T_2-T_1)}\).

α=\(\frac {(2R_0-R_0)}{R_0(T-0)} = \frac {1}{T}\).

T=\(\frac {1}{\alpha}\)

= \(\frac {1}{3.9}\) x 10^-3 ^oC^-1

= 256^oC.

Therefore, the required temperature is 256^oC.