Assume that the thermal conductivity of copper is twice that of aluminium and four times that of brass. Three metal rods made of copper, aluminium and brass are each 15 cm long and 2 cm in diameter. These rods are placed end to end, with aluminium between the other two. The free ends of the copper and brass rods are maintained at `100^@C` and `0^@C` respectively. The system is allowed to reach the steady state condition. Assume there is no loss of heat anywhere.
When steady state condition is reached everywhere, which of the following statement is true?

Options

A. No heat is transmitted across the copper–aluminium or aluminium–brass junctions.
B. More heat is transmitted across the copper–aluminium junction than across the aluminium–brass junction
C. More heat is transmitted across the aluminium–brass junction than the copper–aluminium junction
D. Equal amount of heat is transmitted at the copper–aluminium and aluminium–brass junctions

Answer

D

Explanation

Under steady state conditions, the temperatures at all sections in the system remain constant and maintain a constant temperature gradient for a given material. The temperature gradient in copper, aluminium and brass will not be same however, the rate of heat conducted across all sections whether in copper or aluminium or brass will be the same.