Q.1
In Milikan's oil drop experiment a small, spherical oil drop of radius r is moving in a medium of density ρ with an instantaneous speed v. The viscous force F is [ MPPMT 1989]
  • a)6πηrv
  • b) ηrv
  • c)6η/rv
  • d)6πηrv/ρ
Q.2
Two wires A and B are of the same material. Their lengths are in the ratio 1 :2 and the diameter are in the ratio 2:If they are pulled by the same force, then increase in length will be in the ratio [ CBSE-PMT 1988]
  • a) 2:1
  • b) 1:4
  • c) 1:8
  • d) 8: 1
Q.3
When an elastic material with Young's modulus Y is subjected to stretching stress S, elastic energy stored per unit volume of the material is [1989]
  • a) YS/2
  • b) S2Y/2
  • c) S2/2Y
  • d) S/2Y
Q.4
The terminal velocity vt of a small steel ball of radius r falling under gravity through a column of a viscous liquid of coefficient of viscosity depends on mass of the ball m, acceleration due to gravity g, coefficient of viscosity η and radius r. Which of the following relations is dimensionally correct ? [1992]
  • a)
    ch-8_qn-4choice_img_no1.png
  • b)
    ch-8_qn-4choice_img_no2.png
  • c)
    ch-8_qn-4choice_img_no3.png
  • d)
    ch-8_qn-4choice_img_no4.png
Q.5
The angle of contact between pure water and pure glass, is
  • a) 0°
  • b) 45°
  • c) 90°
  • d) 1350°
Q.6
For a given material, the Young's modulus is 2.4 times that of rigidity modulus. Its Poisson ratio is [ EAMCET 1990]
  • a) 2.4
  • b) 1.2
  • c) 0.4
  • d) 0.2
Q.7
A rectangular block of mass m and area of cross-section A floats in a liquid of density ρ. if it is given a small vertical displacement from equilibrium it undergoes oscillation with a time period T. Then
  • a) T ∝ 1/√A
  • b) T ∝ 1/ρ
  • c)T ∝ 1/√m
  • d)T ∝√ρ
Q.8
A soap bubble has radius r and volume V. If the excess pressure inside the bubble is P. Then PV is proportional to [ AFMC 1997]
  • a) r
  • b)r2
  • c)r3
  • d)r4
Q.9
A ball is falling in a lake of depth 200m creates a decrease of 0.1% in its volume at the bottom. The bulk modulus of the material of the ball will be ..[ CBSE-PMT 1997]
  • a) 19.6 ×10⁻⁸ N/m²
  • b) 19.6 ×10¹⁰ N/m²
  • c) 19.6 ×10⁻¹⁰ N/m²
  • d) 19.6 ×10⁸ N/m²
Q.10
The kinetic energy of one gram molecule of a gas at normal temperature and pressure is (R=8.31 J/ mole K) [ AFMC 1998]
  • a)3.4×103
  • b) 2.97×103
  • c)1.2×103
  • d)0.66×103
Q.11
A big drop of radius R is formed by 1000 small droplets of water, the radius of small drop is [ AFMC 1998]
  • a) R/10
  • b) R/100
  • c)R/500
  • d)R/1000
Q.12
The rain drops are spherical shape due to [AFMC 1999]
  • a) residual pressure
  • b) thrust on the drop
  • c) surface tension
  • d) viscosity
Q.13
10 gm of ice cubes at 0°C are released in a tumbler (water equivalent 55 g) at 40°C. Assuming that negligible heat is taken from the surroundings, the temperature of water in the tumbler becomes nearly (L=80 cal/g) [1988]
  • a)31°C
  • b) 22°C
  • c)19°C
  • d)15°C
Q.14
The two ends of a rod of length L and a uniform cross-sectional area A are kept at two temperatures T1 and T2 (T1 > T2). The rate of heat transfer, dQ/dt through the rod in a steady state is given by:
  • a)
    ch-8_qn-14choice_img_no1.png
  • b)
    ch-8_qn-14choice_img_no2.png
  • c)
    ch-8_qn-14choice_img_no3.png
  • d)
    ch-8_qn-14choice_img_no4.png
Q.15
A cylindrical metallic rod in thermal contact with two reservoirs of heat at its two ends conducts an amount of heat Q in time t. The metallic rod is melted and the material is formed into a rod of half the radius of the original rod. What is the amount of heat conducted by the new rod, when placed in thermal contact with the two reservoirs in time t? [ CBSE-PMT 2010]
  • a) Q/4
  • b) Q/16
  • c)2Q
  • d)Q/2
Q.16
Thermal capacity of 40 g of aluminium (s=0.2 cal /gK) is [ CBSE-PMT 1990]
  • a) 168joule/ °C
  • b) 672joule/°C
  • c) 840joule/°C
  • d) 33.3 joule/°C
Q.17
If the temperature of the sun is doubled, the rate of energy received on earth will be increased by a factor of [ CBSE-PMT 1993]
  • a)2
  • b) 4
  • c)8
  • d)16
Q.18
A body cools from 50.0°C to 48°C in 5s. How long will it take to cool from 40.0°C to 39°C? Assume the temperature of surroundings to be 30.0°C and Newton's law of cooling to be valid, [ CBSE-PMT 1994]
  • a) 2.5s
  • b) 10s
  • c)20s
  • d) 5s
Q.19
A beaker full of hot water is kept in a room. If it cools from 80°C to 75°C in t1 minutes, from 75° C to 70°C in t2 minutes and from 70°C to 65°C in t3 minutes, then [ CBSE-PMT 1995]
  • c)t1
  • d)t1 >t2 > t3
  • a)t₁=t₂=t₃
  • b)t₁ < t₂=t₃
Q.20
The radiant energy from the sun, incident normally at the surface of earth is 20 k cal/ m2 min. What would have been the radiant energy, incident normally on the earth, if the sun had a temperature, twice of the present one? [ CBSE-PMT 1998]
  • a) 160kcal/m2min
  • b) 40kcal/m2min
  • d) 80kcal/m2min
  • c) 320k cal/m² min
Q.21
If 1 g of steam is mixed with 1 g of ice, then the resultant temperature of the mixture is [ CBSE-PMT 1999]
  • a)270°C
  • b) 230°C
  • c)100°C
  • d)50°C
Q.22
The presence of gravitational field is required for the heat transfer by.... [ CBSE-PMT 2000]
  • a) conduction
  • b) stirring of liquids
  • c)natural convection
  • d)radiation
Q.23
If λm denotes the wavelength at which the radiative emission from a black body at a temperature T K is maximum, then [2004]
  • a)λm ∝ T-1
  • b) λm ∝ T4
  • c)λm independent of T
  • d) λm ∝ T1
Q.24
On a new scale of temperature (which is linear) and called the W scale, the freezing and boiling points of water are 39° W and 239° W respectively. What will be the temperature on the new scale, corresponding to a temperature of 39°C on the Celsius scale? [ CBSE-PMT 2008]
  • a) 78° W
  • b) 117°W
  • c)200° W
  • d) 139°W
Q.25
The coefficient of linear expansions of brass and steel are α1 and α2 respectively. When we take a brass rod of length l1 and a steel rod of length l2 at 0°C, then the difference in their lengths (l2 –l1) will remain the same at all temperatures if [ CBSE-PMT 1999]
  • d)α1 l22=α2 l12
  • a)α1 l₁=α2 l₂
  • b) α1 l₂=α2 l₁
  • c)α12 l₂=α22 l₁
Q.26
Assuming the sun to have a spherical outer surface of radius r, radiating like a black body at temperature t°C, the power received by a unit surface, (normal to the incident rays) at a distance R from the center of the sun is…. [ CBSE-PMT 2007]where σ is the Stefan's constant.
  • a)
    ch-8_qn-28choice_img_no1.png
  • b)
    ch-8_qn-28choice_img_no2.png
  • c)
    ch-8_qn-28choice_img_no3.png
  • d)
    ch-8_qn-28choice_img_no4.png
Q.27
A black body at 227°C radiates heat at the rate of 7 cals/cm2s. At a temperature of 727°C, the rate of heat radiated in the same units will be: [ CBSE-PMT 2009]
  • a)50
  • b) 112
  • c)80
  • d)60
Q.28
Radiation from which of the following sources, approximates black body radiation best? [ CBSE-PMT 2002]
  • a) A tungsten lamp
  • b) Sodium flame
  • c)Hot lamp black
  • d)A hole in a cavity, maintained at constant temperature
Q.29
A black body at 1227°C emits radiations with maximum intensity at a wavelength of 5000Å. If the temperature of the body is increased by 1000°C, the maximum intensity will be observed at [2006]
  • a) 5000 Å (Angstrom)
  • b) 6000 Å (Angstrom)
  • c) 3000 Å (Angstrom)
  • d)4000 Å (Angstrom)
Q.30
Which of the following circular rods (given radius r and length l), each made of the same material and whose ends are maintained at the same temperature will conduct most heat? [ CBSE-PMT 2005]
  • a) r=r0 ; l=l0
  • b) r=2r0 ; l=l0
  • c) r=r0 ; l=2l0
  • d) r=2r0 ; l=2l0
0 h : 0 m : 1 s