Q: If the length of a pendulum rod increases due to heat, the time period of the pendulum will?
Answer: Increase
Explanation: 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.
Q: Among these solids, which generally shows the greatest linear expansion for the same temperature rise?
Answer: Aluminium
Explanation: 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.
Q: Real expansion of a liquid refers to?
Answer: Actual increase in volume of the liquid itself
Explanation: 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.
Q: A liquid-in-glass thermometer primarily works on the principle of?
Answer: Thermal expansion of a liquid
Explanation: 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.
Q: Which statement about the coefficient of expansion is generally correct?
Answer: It can vary with temperature and is treated constant over small ranges
Explanation: 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.
Q: If a metal rod is heated but its ends are rigidly fixed, the rod develops?
Answer: Thermal stress
Explanation: 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.
Q: A heated rod whose expansion is completely prevented will experience stress that is mainly?
Answer: Compressive
Explanation: 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.
Q: For a gas at constant pressure, the volume is directly proportional to?
Answer: The absolute temperature (in kelvin)
Explanation: 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.
Q: Expansion loops are provided in long steam pipes mainly to?
Answer: Allow thermal expansion safely
Explanation: 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.
Q: A material known for very low thermal expansion and used in precision instruments is?
Answer: Invar
Explanation: 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.