Answer:
a. 4 J/s
Explanation:
Fourier's law states for the case in which there is stationary heat flow in only one direction, that is, linearly, the heat transmitted per unit of time is proportional to the temperature difference:
[tex]\frac{Q}{t}\propto \Delta T[/tex]
When the temperature at one end is 100°C and at the other is 20°C, we have:
[tex]\Delta T_1=100^\circ C-20^\circ C\\\Delta T_1=80^\circ C[/tex]
If the temperature of the hotter end is [tex]80^\circ C[/tex], we have:
[tex]\Delta T_2=100^\circ C-80^\circ C\\\Delta T_2=20^\circ C[/tex]
So:
[tex]\Delta T_1=4\Delta T_2\\\Delta T_2=\frac{\Delta T_1}{4}[/tex]
Finally, we calculate the rate of heat transfer:
[tex]\frac{Q_2}{t_2}=\frac{\frac{Q_1}{t_1}}{4}\\\\\frac{Q_2}{t_2}=\frac{16\frac{J}{s}}{4}\\\frac{Q_2}{t_2}=4\frac{J}{s}[/tex]
