A copper wire (temperature coefficient of resistance at 20 ) is to be connected in…

PHYSICS · Subjective · CBSE · Physics · Current Electricity · Current Electricity

Problem

A copper wire (temperature coefficient of resistance

\alpha_{cu} = 4.0 \times 10^{-3}\,^{\circ}\text{C}^{-1}

at 20

\,^{\circ}\text{C}

) is to be connected in series with a carbon resistor (temperature coefficient of resistance

\alpha_{c} = -5.0 \times 10^{-4}\,^{\circ}\text{C}^{-1}

at 20

\,^{\circ}\text{C}

). The combination must have a resistance of 20

\Omega

at 20

\,^{\circ}\text{C}

and be nearly independent of temperature for small temperature changes. Calculate the resistance of the carbon resistor at 20

\,^{\circ}\text{C}

that will satisfy this condition.