Exams › JEE Main › Physics

Three rods made of copper, brass, and steel are joined to make a Y-shaped arrangement. Each rod has a cross-sectional area of 4 cm². The copper end is kept at 100°C, while the brass and steel ends are maintained at 0°C. The lengths of the copper, brass, and steel rods are 46 cm, 13 cm, and 12 cm respectively. The rods are insulated from the surroundings except at their ends. If the thermal conductivities of copper, brass, and steel are 0.92, 0.26, and 0.12 in CGS units, respectively, the heat current through the copper rod is:

1. 1.2 cal/s
2. 2.4 cal/s
3. 4.8 cal/s
4. 6.0 cal/s

Correct answer: 4.8 cal/s

Solution

The heat current through the copper rod can be calculated using Fourier's law of heat conduction, which takes into account the thermal conductivity, cross-sectional area, and temperature difference across the rod. Given the values for copper's thermal conductivity, the cross-sectional area, and the temperature difference between the ends, the calculated heat current results in 4.8 cal/s, making it the correct option.

Related JEE Main Physics questions

• A cube initially at 0°C is subjected to the same external pressure P on all its faces, causing it to be compressed. How much must its temperature be increased so that the cube regains its original size? The bulk modulus of the cube material is B and its coefficient of linear expansion is α.
• If λm represents the wavelength at which a black body emits radiation most strongly at temperature T K, then which relation is true?
• Which of the following statements about heat transfer is/are incorrect?
• A composite wall consists of two slabs, A and B, of equal thickness but made of different materials. Their thermal conductivities satisfy K_A = 3K_B. If the total temperature difference across the wall is 20°C, then in steady thermal equilibrium:
• An evacuated bulb contains a filament that is 10 cm long and 0.2 mm in diameter. If its emissivity is 0.2, determine the radiant power emitted by the filament at 2000 K. Take σ = 5.67 × 10⁻⁸ W/m² K⁴.
• A rectangular solid is raised in temperature from 0°C to 100°C. If its length increases by 0.10% over this interval, what is the corresponding percentage increase in its volume?

⚔️ Practice JEE Main Physics free + battle 1v1 →