When a metal bar is cooled, then which one of these staments is correct.

With reference to alkali metals which one of the following statements is correct?

When a metal bar is heated, the increase in length is greater, if

Five vectors, vecX, vecY, vecZ, bar (OB) and bar (AO) are connected as shown in figure. If bar( OB) = bar (AO), then which one of the following option is correct?

Why a gas is cooled when expanded?

If there is one hollow metallic tube which carries current uniformly distributed over its surface, which of the statements is correct?

When the air cools, its density :