Exams › JEE Main › Physics

One end of a conducting rod is held at 50 deg C while the other end keeps ice melting at 0 deg C. The rate of melting of ice is doubled if:

1. the hot-end temperature is made 200 deg C and the cross-sectional area is doubled
2. the hot-end temperature is made 100 deg C and the length is made four times
3. the cross-sectional area is halved and the length is doubled
4. the hot-end temperature is made 100 deg C and both the cross-sectional area and length are doubled

Correct answer: the hot-end temperature is made 100 deg C and both the cross-sectional area and length are doubled

Solution

Heat current = kA*deltaT/L; for option D the factor is (100/50)*(2)*(1/2) = 2, exactly doubling the rate.

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 →