Choose the correct statements from the following:

Options

A. A temperature change which increases the length of a steel rod by `0.1%` will increase its volume by nearly `0.3%`
B. The specific heat of a solid is different when the solid is heated at (i) constant pressure and (ii) the constant volume
C. the thermal conductivity of air being less than that for wool, we prefer wool to air for thermal insulation
D. When the distance between two fixed points is measured with a steel tape, the observed reding will be less on a hot day than on a cold day

Answer

A, B, D

Explanation

Statement (a) is correct vecause the coefficient of volume expansion is very neary three times the coefficient of linear expansion,
Statement (b) is also correct. When a solid is heated at constant pressure, it does expand a little and some heat is required for doing the mechanical work associated with this expansion. The difference between the two specific heats (at constant pressure and at constant volume) is small enough to be generally neglected for solids and liquids. This difference is large for gases.
Statement (c ) is incorrect. The thermal conductivity of air is lwss than that of wool. Yet we prefer wool which traps pockets of air between its fibres. There air pockets cannot carry heat by convection either.
statemetn (d ) is correct because of the expansion of steel tape on a hot day, the markings on the tape would be farther apart than on a cold day.