In Searle's method for finding the conductivity of metals, how does the temperature gradient vary along the bar?
A. Is greater near the hot end
B. Is greater near the cold end
C. Is the same at all points along the bar
D. Increases as we go from hot end to cold end

Hint: A temperature gradient is the change in temperature over a specified distance between two isothermal surfaces or two points in a material. When there is a change in temperature, this causes differences in air pressure between the two points. The unit of the temperature gradient is kelvin per meter.

Complete step by step solution:
Searle's bar method is an experimental procedure to measure the thermal conductivity of the given material. A bar of material is heated by steam on one side (end) and the other side (end) is cooled down by the water while the length of the bar is thermally insulated.

This is done until the temperature gradient at all the points along the bar becomes the same. That is in the steady state the difference in the temperature of a material is the same at all points. Therefore, the temperature gradient along the bar is the same at all points.

Hence, option C is the correct answer.

Note:Here in the given question it is essential to remember the definition of the temperature gradient and how it varies in a given material. Searle’s double bar experiment is one in which we are going to determine the thermal conductivity of a material.