NEET Physics Thermal Properties of Matter MCQs Set A

Question.  A uniform metallic rod rotates about its perpendicular bisector with constant angular speed. If it is heated uniformly to raise its temperature slightly
(a) its speed of rotation decreases
(b) its speed of rotation increases
(c) its speed of rotation remains same
(d) its speed increases because its moment of inertia increases

Answer: A

Question.  An aluminium sphere is dipped into water. Which of the following is true?
(a) Buoyancy will be less in water at 0°C than that in water at 4°C
(b) Buoyancy will be more in water at 0°C than that in water at 4°C
(c) Buoyancy in water at 0°C will be same as that in water at 4°C
(d) Buoyancy may be more or less in water at 4°C depending on the radius of the sphere

Answer: A

Question. As the temperature is increased, the period of a pendulum
(a) increases as its effective length increases even though its centre of mass still remains at the centre of the bob
(b) decreases as its effective length increases even though its centre of mass still remains at the centre of the bob
(c) increases as its effective length increases due to shifting to centre of mass below the centre of the bob
(d) decreases as its effective length remains same but the centre of mass shifts above the centre of the bob

Answer: A

Question. Heat is associated with
(a) kinetic energy of random motion of molecules
(b) kinetic energy of orderly motion of molecules
(c) total kinetic energy of random and orderly motion of molecules
(d) kinetic energy of random motion in some cases and kinetic energy of orderly motion in other

Answer: A

Question.  A sphere, a cube and a thin circular plate, all of same material and same mass are initially heated to same high temperature
(a) Plate will cool fastest and sphere the slowest
(b) Cube will cool fastest and plate the slowest
(c) Sphere will cool fastest and cube the slowest
(d) Plate will cool fastest and cube the slowest

Answer: A

Question.  Steam at 100°C is passed into 20 g of water at 10°C. When water acquires a temperature of 80°C, the mass of water present will be: [Take specific heat of water = 1 cal g^{– 1} °C^{– 1} and latent heat of steam = 540 cal g^{– 1}]
(a) 24 g
(b) 31.5 g
(c) 42.5 g
(d) 22.5 g

Answer: A

Question. Certain quantity of water cools from 70°C to 60°C in the first 5 minutes and to 54°C in the next 5 minutes. The temperature of the surroundings is:
(a) 45°C
(b) 42°C
(c) 20°C
(d) None of these

Answer: A

Question. If the temperature of the sun were to increase from T to 2T and its radius from R to 2R, then the ratio of the radiant energy received on earth to what it was previously will be
(a) 64
(b) 4
(c) 16
(d) 32

Answer: A

Question.  A crystal has a coefficient of expansion 13×10^–7 in one direction and 231 × 10^–7 in every direction at right angles to it. Then the cubical coefficient of expansion is
(a) 475 × 10^–7
(b) 462 × 10^–7
(c) 244 × 10^–7
(d) 257 × 10^–7

Answer: A

Question.  Three rods of Copper, Brass and Steel are welded together to form a Y shaped structure. Area of cross - section of each rod = 4 cm². End of copper rod is maintained at 100ºC where as ends of brass and steel are kept at 0ºC. Lengths of the copper, brass and steel rods are 46, 13 and 12 cms respectively. The rods are thermally insulated from surroundings excepts at ends. Thermal conductivities of copper, brass and steel are 0.92, 0.26 and 0.12 CGS units respectively. Rate of heat flow through copper rod is:
(a) 4.8 cal/s
(b) 6.0 cal/s
(c) 2.4 cal/s
(d) 1.2 cal/s

Answer: A

Question.  The value of coefficient of volume expansion of glycerine is 5 × 10^-4 K^-1. The fractional change in the density of glycerine for a rise of 40°C in its temperature, is:
(a) 0.020
(b) 0.025
(c) 0.010
(d) 0.015

Answer: A

Question.  A piece of ice falls from a height h so that it melts completely. Only one-quarter of the heat produced is absorbed by the ice and all energy of ice gets converted into heat during its fall. The value of h is : [Latent heat of ice is 3.4 × 10⁵ J/kg and g = 10 N/kg]
(a) 136 km 
(b) 68 km
(c) 544 km
(d) 34 km

Answer: A

Question. Steam is passed into 22 g of water at 20°C. The mass of water that will be present when the water acquires a temperature of 90°C is (Latent heat of steam is 540 cal/gm)
(a) 24.8 gm
(b) 24 gm
(c) 36.6 gm
(d) 30 gm

Answer: A

Question.  Two spheres of different materials one with double the radius and one-fourth wall thickness of the other are filled with ice. If the time taken for complete melting of ice in the larger sphere is 25 minute and for smaller one is 16 minute, the ratio of thermal conductivities of the materials of larger spheres to that of smaller sphere is
(a) 8 : 25
(b) 25 : 8
(c) 5 : 4
(d) 4 : 5

Answer: A

Question.  A spherical black body with a radius of 12 cm radiates 450 watt power at 500 K. If the radius were halved and the temperature doubled, the power radiated in watt would be
(a) 1800
(b) 225
(c) 1000
(d) 450

Answer: A

Question.  A beaker is filled with water at 4°C. At one time the temperature is increased by few degrees above 4°C and at another time it is decreased by a few degrees below 4°C. One shall observe that:
(a) water overflows in both the cases
(b) in second case water over flows while in first case its comes down
(c) in first case water flows while in second case its level comes down
(d) the level remains constant in each case

Answer: A

Question.  dropped in a copper calorimeter of mass 100 gm, filled with 170 gm of water at room temperature. Subsequently, the temperature of the system is found to be 75°C. T is given by (Given : room temperature = 30° C, specific heat of copper = 0.1 cal/gm°C
(a) 885° C
(b) 800°C
(c) 825°C
(d) 1250°C

Answer: A

Question.  During vapourisation 
I. change of state from liquid to vapour state occurs.
II. temperature remains constant.
III. both liquid and vapour states coexist in equilibrium.
IV. specific heat of substance increases.
Correct statements are
(a) I , II and III
(b) II, III and IV
(c) I, II and IV
(d) I, III and IV

Answer: A

Question. Assertion : It is hotter over the top of a fire than at the same distance on the sides.
Reason : Air surrounding the fire conducts more heat upwards
(a) Assertion is correct, reason is incorrect
(b) Assertion is incorrect, reason is correct.
(c) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(d) Assertion is correct, reason is correct; reason is a correct explanation for assertion

Answer: A

Question.   Water of volume 2 litre in a container is heated with a coil of 1 kW at 27°C. The lid of the container is open and energy dissipates at rate of 160 J/s. In how much time temperature will rise from 27°C to 77°C? [Given specific heat of water is 4.2 kJ/kg]
(a) 8 min 20 s
(b) 7 min
(c) 6 min 2 s
(d) 14 min

Answer: A

Question.   A piece of ice (heat capacity = 2100 J kg^–1 °C^–1 and latent heat = 3.36 × 105 J kg^–1) of mass m grams is at –5°C at atmospheric pressure. It is given 420 J of heat so that the ice starts melting. Finally when the ice-water mixture is in equilibrium, it is found that 1 gm of ice has melted. Assuming there is no other heat exchange in the process, the value of m is
(a) 8
(b) 4
(c) 2
(d) 5

Answer: A

Question.   A solid copper cube of edges 1 cm each is suspended in an evacuated enclosure. Its temperture is found to fall from 100°C to 99°C in 100 s. Another solid copper cube of edges 2 cm, with similar surface nature, is suspended in a similar manner. The time required for this cube to cool from 100°C to 99°C will be approximately
(a) 200 s
(b) 400 s
(c) 50 s
(d) 25 s

Answer: A

Question.  A cube, a pyramid (with faces identical) and a sphere (all of  them hollow) are made from the same material and have equal mass and bound equal volume. They are heated to the same temperature and then left to cool. After some time,
1. sphere will have the highest temperature
2. pryamid will have the highest temperature.
3. cube will have the lowest temperature.
4. sphere will have the lowest temperature.
5. pyramid will have the lowest temperature
Correct option will be :
(a) 1 and 5
(b) 2 and 4
(c) 3 and 1
(d) 2 and 3

Answer: A