Physics Times 07.2019

2. Assume that a drop of liquid evaporates by
   decrease in its surface energy, so that its
   temperature remains unchanged. What should
   be the minimum radius of the drop for this to
   be possible? The surface tension is T, density
   of liquid is  and L is its latent heat of
   vaporisation. [2013]
   (a) L T/ (b) T/L
   (c) T/L (d) 2 /T L


3. 100 g of water is heated from 30 to50 . C C

Ignoring the slight expansion of the water, the
change in its internal energy is (specific heat
of water is 4184 J/kg K) [2011]
(a) 8.4 kJ (b) 84 kJ (c) 2.1 kJ (d) 4.2 kJ
4.The specific heat capacity of a metal at low
temperature (T) is given as

 

[2013]

[2011]

4.

[2011]

3

(^1132)
p 400
C kHK kg    T
  
A 100 gram vessel of this metal is to be cooled
from 20 to 4 K K by a special refrigerator
operating at room temperature ^27 C. The
amount of work required to cool the vessel is
[2011]
(a) Greater than 0.148 kJ
(b) Between 0.148 kJ and 0.028 kJ
(c) Less than 0.028 kJ
(d) Equal to 0.002 kJ
KINETIC THEORY OF GASES
[ONLINE QUESTIONS]

1. a 2. d 3. c 4. d 5. d


2. a 7. b 8. c 9. c

[OFFLINE QUESTIONS]

1. b 2. a 3. b 4. c 5. c


2. a 7. a 8. a 9. b

CALORIMETRY [ONLINE QUESTIONS]

1. d 2. b 3. c 4. d 5. b

[OFFLINE QUESTIONS]

1. d 2. d 3. a 4. d

KINETIC THEORY OF GASES

[ONLINE QUESTIONS]

1.Sol: Energy associated with N moles of

diatomic gas,

2.Sol: The ratio of specific heats at constant

pressure

KINETIC THEORY OF GASES

[ONLINE QUESTIONS]

[OFFLINE QUESTIONS]

CALORIMETRY [ONLINE QUESTIONS]

[OFFLINE QUESTIONS]

5

i 2

U N RT

Energy associated with n moles of mono

atomic gas

3

2

n RT

Total energy when n moles of diatiomic gas

converted into monoatomic

( ) 2^3 ( )^5

f 2 2

U   n RT N n RT

1 5

2 2

 nRT NRT

Change in total kinetic energy of the gas

1

2

U nRT

( )CP and constant volume ( )CV

P 1 2

V

C

C F

     

 

where F is degree of freedom

1 2 7

5 5

P

V

C

C

   

  

3.Sol: Pressure,

(^12)
3
P mNvrms
V
 ( )^2
P vrms T
So, force ( rms)^2
i.e., Value of q=1
4.Sol: According to Dulong-Petit law many
solids at room temperature
KINETIC THEORY OF GASES
[ONLINE QUESTIONS]
1.Sol:
2.Sol:
3.Sol:
4.Sol:
v T
CV3 .R For
solids when heat is given their volume
approximately remain constant.