A heat source at T = 10 3   K is connected to another heat reservoir at T = 10 2   K by a copper…

Given,

Temperature of heat source, $T_{\mathrm{H}}={10}^3 \mathrm{K}$,

Temperature of heat reservoir, $T_{\mathrm{L}}={10}^2 \mathrm{K}$,

Conductivity of copper $K=0.1 \mathrm{W} {\mathrm{K}}^{-1}{\mathrm{m}}^{-1}$

From the equation of steady-state heat flow,

$\frac{dQ}{dt}=\frac{KA∆T}{L}$

Heat energy flux can be defined as the rate of heat energy transfer through a given surface.

$\frac{1}{A}\left(\frac{dQ}{dt}\right)=K\times \frac{1000-100}{1}=90 \mathrm{W} {\mathrm{m}}^{-2}$