46. Displacement vector D, electric field E and polarisation vector, P are related as (1) D-EE- (2) D=E+ P 121K (3) DE, (K-1) E+ P (4) = E+P 47. A gas of molecules, each having mass m, is at rest in thermal equilibrium at the absolute temperature T. If v and vy are cartesian components of velocity of a molecule, what is the mean value of (v,+bv), where b is a constant? 3kT (1) (1 + b) (2) m kT (3) (1+b) (4) m 8kT (1+b)2 m 3kT m 48. Choose the wrong Maxwell's relations for thermodynamical variables. OP (1) avs (as) as (2) OTV (OT (3) S as P as (4) (9)--(Y) 49. The density of liquid Helium is maximum at (1) -4C (3) 2.19 K (2) 4.2 K (4) OK 50. The enthalpy of a gas before and after Joule-Tomson expansion are 80 cal and 120 cal respectively. If enthalpy of emergent liquid is 40 cal, then what fraction of gas will liquidify? (1) 25% (3) 50% (2) 43% (4) 63%