Expansion — Set 2

Correct Answer: A. Increase

Time period of a pendulum is proportional to the square root of its length. Heating increases the rod length by thermal expansion. So the time period increases and the clock can run slow.

Correct Answer: B. Aluminium

Different solids have different linear expansion coefficients. Aluminium typically has a larger α than steel and glass. Invar has a very small α compared to common metals.

Correct Answer: B. Actual increase in volume of the liquid itself

Real expansion is the true increase in liquid volume on heating. It does not include the expansion of the container. Apparent expansion is what you observe in an expanding container.

Correct Answer: B. Thermal expansion of a liquid

Liquids expand when heated and contract when cooled. The change in volume moves the liquid level in a narrow tube. This change is calibrated to measure temperature.

Correct Answer: A. It can vary with temperature and is treated constant over small ranges

Expansion coefficients can change with temperature. For many calculations, they are assumed constant over a small temperature interval. The value also depends strongly on the material.

Correct Answer: B. Thermal stress

Heating tries to increase the rod length by expansion. If expansion is prevented, internal forces appear. This produces thermal stress, often estimated using stress = YαΔT.

Correct Answer: A. Compressive

The rod wants to expand, but constraints oppose that change. The constraints push inward against the attempted increase in length. So the stress developed is compressive for heating.

Correct Answer: B. The absolute temperature (in kelvin)

At constant pressure, gases expand uniformly with temperature in ideal behavior. This is the statement of Charles’ law. It says V is proportional to absolute temperature T.

Correct Answer: D. Allow thermal expansion safely

Long pipes expand significantly when heated by hot steam. If the pipe cannot expand, large stress can damage joints. Expansion loops give flexibility to accommodate thermal expansion.

Correct Answer: B. Invar

Invar is an alloy designed to have a very small expansion coefficient. That makes its length nearly stable with temperature changes. It is commonly used in precision measuring devices.