CBSE Class 11 Physics Thermal Properties Of Matter Assignment

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) 200°W
(b) 139°W
(c) 78°W
(d) 117°W 
Answer. D

Question. Mercury thermometer can be used to measure temperature upto
(a) 260°C
(b) 100°C
(c) 360°C
(d) 500°C
Answer. C

Question. A Centigrade and a Fahrenheit thermometer are dipped in boiling water. The water temperature is lowered until the Fahrenheit thermometer registers 140°F. What is the fall in temperature as registered by the centigrade thermometer?
(a) 80°C
(b) 60°C
(c) 40°C
(d) 30°C
Answer. C

Question. A copper rod of 88 cm and an aluminium rod of unknown length have their increase in length independent of increase in temperature. The length of aluminium rod is (αCu = 1.7 × 10^–5 K^–1, αAl = 2.2 × 10^–5 K^–1)
(a) 68 cm
(b) 6.8 cm
(c) 113.9 cm
(d) 88 cm
Answer. A

Question. Coefficient of linear expansion of brass and steel rods are α₁ and α₂. Lengths of brass and steel rods are l₁ and l₂ respectively. If (l₂ – l₁) is maintained same at all temperatures, which one of the following relations holds good?
(a) α₁² l₂ = α₂² l₁
(b) α₁ l₁ = α₂ l₂
(c) a₁l₂ = a₂l₁
(d) a₁l₂² = a₂l₁²
Answer. B

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

Question. The density of water at 20°C is 998 kg/m3 and at 40°C is 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. A

Question. Thermal capacity of 40 g of aluminium
(s = 0.2 cal/g K) is
(a) 168 J/K
(b) 672 J/K
(c) 840 J/K
(d) 33.6 J/K
Answer. D

Question. Two identical bodies are made of a material for which the heat capacity increases with temperature. One of these is at 100°C, while the other one is at 0°C. If the two bodies are brought into contact, then, assuming no heat loss, the final common temperature is
(a) 50°C
(b) more than 50°C
(c) less than 50°C but greater than 0°C
(d) 0°C
Answer. B

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) 34 km
(d) 544 km 
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. D

Question. If 1 g of steam is mixed with 1 g of ice, then resultant temperature of the mixture is
(a) 100°C
(b) 230°C
(c) 270°C
(d) 50°C
Answer. A

Question. 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 nearely (L = 80 cal/g)
(a) 31°C
(b) 22°C
(c) 19°C
(d) 15°C
Answer. B

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) 450
(b) 1000
(c) 1800
(d) 225
Answer. C

Question. A black body is at a temperature of 5760 K.The energy of radiation emitted by the body at wavelength 250 nm is U₁, at wavelength 500 nm is U₂ and that at 1000 nm is U₃. Wien’s constant, b = 2.88 × 106 nm K. Which of the following is correct?
(a) U₁ > U₂
(b) U₂ > U₁
(c) U₁ = 0
(d) U₃ = 0
Answer. B

Question. The two ends of a metal rod are maintained at temperatures 100°C and 110°C. The rate of heat flow in the rod is found to be 4.0 J/s. If the ends are maintained at temperatures 200°C and 210°C, the rate of heat flow will be
(a) 8.0 J/s
(b) 4.0 J/s
(c) 44.0 J/s
(d) 16.8 J/s 
Answer. B

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) Kirchhoff’s Law
(b) Newton’s Law of cooling
(c) Stefan’s Law
(d) Wien’s displacement Law 
Answer. D

Question. Two metal rods 1 and 2 of same lengths have same temperature difference between their ends. Their thermal conductivities are K₁ and K₂ and cross sectional areas A₁ and A₂, respectively. If the rate of heat conduction in 1 is four times that in 2, then
(a) K₁A₁ = 4K₂A₂
(b) K₁A₁ = 2K₂A₂
(c) 4K₁A₁ = K₂A₂
(d) K₁A₁ = K₂A₂
Answer. A

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. A

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) Q/4
(b) Q/16
(c) 2Q
(d) Q/2
Answer. B

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) 50
(b) 112
(c) 80
(d) 60
Answer. B

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. A

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. A

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) r = r₀, l = l₀
(b) r = 2r₀, l =  l₀
(c) r = r₀, l = 2 l₀
(d) r = 2r₀, l = 2 l₀.
Answer. B

Question. Consider a compound slab consisting of two different materials having equal thicknesses and thermal conductivities K and 2K, respectively. The equivalent thermal conductivity of the slab is
(a) 2/3 K
(b) √2 K
(c) 3 K
(d) 4/3 K 
Answer. A

Question. Unit of Stefan’s constant is
(a) watt m² K⁴
(b) watt m²/K⁴
(c) watt/m² K
(d) watt/m²K⁴
Answer. D

Question. For a black body at temperature 727°C, its radiating power is 60 watt and temperature of surrounding is 227°C. If temperature of black body is changed to 1227°C then its radiating power will be
(a) 304 W
(b) 320 W
(c) 240 W
(d) 120 W 
Answer. B

Question. Which of the following is best close to an ideal black body?
(a) black lamp
(b) cavity maintained at constant temperature
(c) platinum black
(d) a lump of charcoal heated to high temperature.
Answer. B

Question. The Wien’s displacement law express relation between
(a) wavelength corresponding to maximum energy and temperature
(b) radiation energy and wavelength
(c) temperature and wavelength
(d) colour of light and temperature.
Answer. A

Question. A cylindrical rod having temperature T₁ and T₂ at its end. The rate of flow of heat Q₁ cal/sec. If all the linear dimension are doubled keeping temperature constant, then rate of flow of heat Q₂ will be
(a) 4Q₁
(b) 2Q₁
(c) Q₁/4
(d) Q₁/2
Answer. B

Question. The radiant energy from the sun, incident normally at the surface of earth is 20 kcal/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?
(a) 320 kcal/m² min
(b) 40 kcal/m² min
(c) 160 kcal/m² min
(d) 80 kcal/m² min
Answer. A

Question. A black body is at a temperature of 500 K. It emits energy at a rate which is proportional to
(a) (500)³
(b) (500)⁴
(c) 500
(d) (500)² 
Answer. B

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) 2 : 1
(b) 8 : 1
(c) 1 : 1
(d) 1 : 8 
Answer. D

Question. If the temperature of the sun is doubled, the rate of energy recieved on earth will be increased by a factor of
(a) 2
(b) 4
(c) 8
(d) 16
Answer. D

Question. A body cools from a temperature 3T to 2T in 10 minutes. The room temperature is T. Assume that Newton’s law of cooling is applicable. The temperature of the body at the end of next 10 minutes will be
(a) 7/4 T
(b) 3/2 T
(c) 4/3 T
(d) T
Answer. B

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) 20°C
(c) 42°C
(d) 10°C 
Answer. A

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) t₁ < t₂ < t₃
(b) t₁ > t₂ > t₃
(c) t₁ = t₂ = t₃
(d) t₁ < t₂ = t₃.
Answer. A