The two ends of a uniform rod of thermal conductivity k are maintained at different but constant temperatures. The temperature gradientat any point on the rod is `(d theta)/(dl)`(equal to the difference in temperature per unit length). The heat flow per unit time per unit cross-section of the rod is `l` then which of the following statements is/are correct:

Options

A. `(dtheta)/(dl)` is the same for all points on the rod
B. I will decrease as we move from higher to lower temperature
C. `Ipropk.(dtheta)/(dl)`
D. All the above options are incorrect

Answer

A, C

Explanation

As the two ends of the rod are at constant temperature that means the rod is in steady state of thermal conduction hence throughout the length the temperature gradient will remain constant and in steady state of thermal conduction the rate ofheat flow (heat current) is given by the product of thermal conductivity, cross sectional area and the temperature gradient.