JEE Physics Thermal Properties Of Matter MCQs Set B

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Gravitational force is required for

• a) Convection
• b) Conduction
• c) Radiation
• d) Stirring of liquid

Answer: Convection

Question: Which of the following processes is reversible?

• a) Isothermal compression
• b) Transfer of heat by conduction
• c) Transfer of heat by radiation
• d) Electrical heating of a nichrome wire

Answer: Isothermal compression

Question: Solar constant (S) depends upon the temperature of the Sun (T) as

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Three rods of same dimensions have thermal conductivities 3K, 2K and K. They are arranged as shown, withtheir ends at 100°C, 50°C and 0°C. The temperature of their junction is

• a)

  

• b)

  

• c) 40°C
• d) 75°C

Answer:

Question: If wavelength of maximum intensity of radiation emitted by Sun and Moon are 0.5 × 10^–6 m and 10^–4 m respectively, then the ratio of their temperature is

• a) 200
• b) 100
• c) 150
• d) 500

Answer:  200

Question:

• a) 400 W
• b) 200 W
• c) 100 W
• d) 300 W

Answer: 400 W

Question:

• a) S_A > S_B
• b) S_A = S_B
• c) Both
• d) None of these

Answer: S_A > S_B

Question: Two spheres of same material and radius r and 2r are heated to same temperature and are kept in identical surroundings, ratio of their rate of loss of heat is

• a) 1 : 4
• b) 1 : 6
• c) 1 : 8
• d) 1 : 2

Answer: 1 : 4

Question: Assume that Solar constant is 1.4 kW/m², radius of sun is 7 × 10⁵ km and the distance of earth from centre of sun is 1.5 × 10⁸ km. Stefan’s constant is 5.67 × 10^–8 Wm^–2 K^–4, find the approximate temperature of sun

• a) 5800 K
• b) 16000 K
• c) 15500 K
• d) 8000 K

Answer: 5800 K

Question: If a graph is plotted by taking spectral emissive power along y-axis and wavelength along x-axis then the area below the graph above wavelength axis is

• a) Total intensity of radiation
• b) Solar constant
• c) Emissivity
• d) Diffusivity

Answer: Total intensity of radiation

Question: A spherical black body with  radius 12 cm radiates 450 W power at 500 K. If the radius is halved and temperature is doubled, the power radiated in watt would be

• a) 1800
• b) 900
• c) 450
• d) 225

Answer: 1800

Question: Three rods of same material, same area of cross-section but different lengths 10 cm, 20 cm and 30 cm are connected at a point as shown. What is temperature of junction O?

• a) 16.4°C
• b) 11.5°C
• c) 22°C
• d) 19.2°C

Answer: 16.4°C

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:  A solid cylinder of length L and radius r is heat upto same temperature as that of a cube of edge length a. If both have same material, volume and allowed to cool under similar conditions, then ratio of amount of radiations radiated will be (Neglect radiation emitted from flat surfaces of the cylinder)

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A very thin metallic shell of radius r is heated to temperature T and then allowed to cool. The rate of cooling of shell is proportional to

• a) r ⁰
• b) r²
• c) rT
• d) None of these

Answer: r ⁰

Question:  If an object at absolute temperature (T) radiates energy at rate R, then select correct graph showing the variation of log_e R with log_e(T).

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Two diagonally opposite corners of a square made of a four thin rods of same material, same dimensions are at temperature 40°C and 10°C. If only heat conduction takes place, then the temperature difference between other two corners will be

• a) 0°C
• b) 10°C
• c) 25°C
• d) 15°C

Answer: 0°C

Question: Bottom of a lake is at 0°C and atmospheric temperature is –20°C. If 1 cm ice is formed on the surface in 24 h, then time taken to form next 1 cm of ice is

• a) 72 h
• b) 48 h
• c) 96 h24 h
• d) 24 h

Answer: 72 h

Question: The power received at distance d from a small metallic sphere of radius r(<

• a) 64p
• b) 32p
• c) 8p
• d) 4p

Answer: 64p

 

More Questions...................................

Question:  A sphere, a cube and a thin circular plate, all made of the same mass and finish are heated to a temperature of 200°C. Which of these objects will cool slowest, when left in air at room temperature?

• a) The sphere
• b) The circular plate
• c) The cube
• d) All will cool at same rate

Answer: The sphere

Question: 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?

• a) 117°W
• b) 200°W
• c) 78°W
• d) 139°W

Answer: 117°W

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: The density of water at 20°C is 998 kg/m³ and at 40°C 992 kg/m³. The coefficient of volume expansion of water is

• a) 3 × 10^–4/°C
• b) 2 × 10–4/°C
• c) 6 × 10^–4/°C
• d) 10^–4/°C

Answer: 3 × 10^–4/°C

Question:  Liquid oxygen at 50 K is heated to 300 K at constant pressure of 1 atm. The rate of heating is constant. Which one of the following graphs represents the variation of temperature with time?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A slab of stone of area 0.36 m² and thickness 0.1 m is exposed on the lower surface to steam at 100°C. A block of ice at 0°C rests on the upper surface of the slab. In one hour 4.8 kg of ice is melted. The thermal conductivity of slab is (Given latent heat of fusion of ice = 3.36 × 10⁵ J kg^–1 )

• a) 1.24 J/m/s/°C
• b) 1.29 J/m/s/°C
• c) 2.05 J/m/s/°C
• d) 1.02 J/m/s/°C

Answer: 1.24 J/m/s/°C

Question: When 1 kg of ice at 0°C melts to water at 0° C, the resulting change in its entropy, taking latent heat of ice to be 80 cal/°C is

• a) 293 cal/K
• b) 273 cal/K
• c) 8 × 104 cal/K
• d) 80 cal/K

Answer: 293 cal/K

Question: If 1 g of steam at 100°C steam is mixed with 1 g of ice at 0°C, then resultant temperature of the mixture is

• a) 100°C
• b) 230°C
• c) 270°C
• d) 50°C

Answer: 100°C

Question: Heat is flowing through two cylindrical rods of the same material. The diameters of the rods are in the ratio 1 : 2 and the lengths in the ratio 2 : 1. If the temperature difference between the ends is same, then ratio of the rate of flow of heat through them will be

• a) 1 : 8
• b) 1 : 1
• c) 8 : 1
• d) 2 : 1

Answer: 1 : 8

Question: A cylindrical rod has temperatures T₁ and T₂ at its ends. The rate of flow of heat is Q (cal/s). If all the linear dimensions are doubled keeping temperatures constant, then rate of flow of heat Q₂ will be

• a) 2Q₁
• b) 4Q₁
• c)

  

• d)

  

Answer: 2Q₁

Question: Two metal rods 1 and 2 of same lengths have same temperature difference between their ends. Their thermal conductivities are K₁ and K₂and cross sectional areas A₁and A₂, respectively. If the rate of heat conductionin 1 is four times that in 2, then

• a) K₁A1= 4K₂A₂
• b) K₁A₁= K₂A₂
• c) K₁A₁= 2K₂A₂
• d) None of these

Answer: K₁A1= 4K₂A₂

Question: Consider two rods of same lengths and different specific heats (S₁, S₂), conductivities (K₁, K₂) and area ofcross-sections (A₁, A₂) and both having temperatures T₁, and T₂ at their ends. If rate of flow of heat due to conduction is equal, then

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: Consider a compound slab consisting of two pieces of same length and different materials having equal thicknesses and thermal conductivities K and 2 K, respectively. The equivalent thermal conductivity of the slab is

• a) 4/3 K
• b) 3K
• c) 2/3 K
• d)

  

Answer: 4/3 K

Question:  Which of the following 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?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:  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?

• a)

  

• b)

  

• c) 2Q
• d)

  

Answer:

Question: Gravitational force is required for

• a) Convection
• b) Conduction
• c) Radiation
• d) Stirring of liquid

Answer: Convection

Question: A black body is at a temperature of 500 K. It emits energy at a rate which is proportional to

• a) (500)⁴
• b) 500
• c) (500)³
• d) 400

Answer: (500)⁴

Question: Which of the following is closest to an ideal black body?

• a) Cavity maintained at constant temperature
• b) Black lamp
• c) Platinum black
• d) A lamp of charcoal heated to high temperature

Answer: Cavity maintained at constant temperature

Question: A black body is at 727°C. It emits energy at a rate which is proportional to

• a) (1000)⁴
• b) (1000)²
• c) (727)⁴
• d) (727)²

Answer: (1000)⁴

Question: For a black body at temperature 727°C, its rate of energy loss is 20 watt and temperature of surrounding is 227°C. If temperature of black body is changed to 1227°C then its rate of energy loss will be

• a)

  

• b) 240 W
• c) 120 W
• d) 304 W

Answer:

Question: 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

• a) 112
• b) 50
• c) 60
• d) 80

Answer: 112

Question:  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

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A black body at 1227°C emits radiations with maximum intensity at a wavelength of 5000 Å. If the temperature of the body is increased by 1000°C, the maximum intensity will be observed at

• a) 3000 Å
• b) 4000 Å
• c) 5000 Å
• d) 6000 Å

Answer:  3000 Å

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: A piece of iron is heated in a flame. It first becomes dull red then becomes reddish yellow and finally turns to white hot. The correct explanation for the above observation is possible by using

• a) Wien's displacement Law
• b) Newton's Law of cooling
• c) Kirchhoff's Law
• d) Stefan's Law

Answer: Wien's displacement Law

Question: The Wien’s displacement law expresses the relation between

• a) Wavelength corresponding to maximum intensity and temperature
• b) Radiation energy and wavelength
• c) Temperature and wavelength
• d) Colour of light and temperature

Answer: Wavelength corresponding to maximum intensity and temperature

Question: We consider the radiation emitted by the human body. Which one of the following statements is correct?

• a) The radiation emitted is in the infra-red region
• b) The radiation is emitted only during the day
• c) The radiation is emitted during the summers and absorbed during the winters
• d) The radiation emitted lies in the ultraviolet region and hence is not visible

Answer: The radiation emitted is in the infra-red region

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question: If the radius of a star is R and it acts as a black body, what would be the temperature of the star, in which the rate of energy production is Q?

• a)

  

• b)

  

• c)

  

• d)

  

Answer:

Question:

• a)

  

• b)

  

• c)

  

• d)

  

Answer: