Q: The radius of metal sphere at room temperature T is R and the coefficient of linear expansion of the metal is α . The sphere heated a little by a temperature ΔT so that its new temperature is T + ΔT. the increase in the volume of the sphere is approximately.

(a) 2 π R α ΔT

(b) 2 π R^{2} α ΔT

(c) 4π R^{3}α ΔT/3

(d) 4π R^{3}α ΔT

Ans: (d)