Exams › JEE Main › Physics

An iron rod and a copper rod are placed side by side. As the temperature changes, the difference between their lengths stays constant at 10 cm. Given the linear expansion coefficients alpha_iron = 1.1 x 10⁻⁵ per deg C and alpha_copper = 1.7 x 10⁻⁵ per deg C, find the length of the iron rod at 0 deg C.

1. 28.3 cm
2. 18.3 cm
3. 33.5 cm
4. 22.7 cm

Correct answer: 28.3 cm

Solution

The difference stays constant only if both rods expand by the same absolute amount, i.e. L_iron*alpha_iron = L_copper*alpha_copper; solving with the 10 cm difference gives the iron rod length about 28.3 cm.

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 →