2. A large number of water drops each of radius r combine to have a drop of radius R. If the surface tension is T and the mechanical equivalent of heat is J, then the rise in temperature will be
(a) 2T/rJ
(b) 3T/RJ
(c) 3T/J[(1/R )-(1/R)]
(d) 2T/J[(1/r)-(1/R)]
Ans. c
(30)