A copper rod is to remove of heat steadily from a hot surface at to a sink at

PHYSICS · Single correct · CBSE · Physics · Thermal Properties of Matter · Thermal Properties of Matter

Problem

A copper rod is to remove

100\,\text{W}

of heat steadily from a hot surface at

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

to a sink at

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

. The rod is

0.20\,\text{m}

long and the thermal conductivity of copper is

400\,\text{W m}^{-1}\,\text{K}^{-1}

. The minimum cross-sectional area needed is (a)

4.2\times10^{-4}\,\text{m}^2

(b)

1.1\times10^{-3}\,\text{m}^2

(c)

5.6\times10^{-4}\,\text{m}^2

(d)

5.6\times10^{-5}\,\text{m}^2