CBSE Questions for Class 11 Engineering Physics Thermal Properties Of Matter Quiz 6 - MCQExams.com

Three rods of same material and having same crosssection have been joined as shown in fig.Each rod is of same length. The left and right rods are kept at 0$$^{o}$$C and 90$$^{o}$$C respectively.The temperature of the junction of the three rods will be
26718_3126d2b55c3d4c8ba797fe475a3cec50.png
  • $$45^{o}C$$
  • $$60^{o}C$$
  • $$30^{o}C$$
  • $$20^{o}C$$
Four identical rods of same material are joined at ends so as to form a square. If the temperature difference at the ends of a diagonal is 100$$^{o}$$C, then the temperature difference across the ends of another diagonal will be
  • $$0^{o}C$$
  • $$25^{o}C$$
  • $$50^{o}C$$
  • $$100^{o}C$$
Choose the correct statements from the following
  • All bodies emit thermal radiations at all temperatures
  • Thermal radiations are electromagnetic waves
  • Thermal radiations are not reflected from a mirror
  • Thermal radiations travel in free space with a velocity of $$3\times 10$$$$^{8}$$ms$$^{-1}$$.
A double-pane window used for insulating a room thermally from outside consists of two glass sheets each of area 1m$$^{2}$$ and thickness $$0.01$$m separated by $$0.05$$m thick stagnant air space.In the steady state, the room-glass interface and the glass-outdoor interface are at constant temperatures of 27$$^{o}$$C and 0$$^{o}$$C respectively.The thermal conductivity of glass is $$0.8$$ and of air 0.08Wm$$^{-1}$$K$$^{-1}$$

The temperature of the outer glass-air interface is
  • $$26.5^{o}C$$
  • $$25.5^{o}C$$
  • $$24.5^{o}C$$
  • $$23.5^{o}C$$
Three cylindrical rods $$A, B, C$$ of equal lengths and equal diameters are joined in series as shown in the figure. Their thermal conductivities are $$2k, k, 0.5k$$ respectively. In the steady state, the free ends of rods $$A$$ and $$C$$ are at 100$$^{o}$$C and 0$$^{o}$$C respectively. Neglect loss of heat from the curved surfaces of rods.
The temperature of the junction between rods $$A$$ and $$B$$ is :

26968_968928ac50024ca385d9649347733f46.png
  • $$55.7^{o}C$$
  • $$65.7^{o}C$$
  • $$75.7^{o}C$$
  • $$85.7^{o}C$$
A double-pane window used for insulating a room thermally from outside consists of two glass sheets each of area 1m$$^{2}$$ and thickness 0.01m separated by 0.05m thick stagnant air space.In the steady state, the room-glass interface and the glass-outdoor interface are at constanttemperatures of 27$$^{o}$$C and 0$$^{o}$$C respectively.The thermal conductivity of glass is 0.8 and of air 0.08Wm$$^{-1}$$K$$^{-1}$$

The temperatures of the inner glass-air interface is
  • $$2.5^{o}C$$
  • $$2.0^{o}C$$
  • $$1.5^{o}C$$
  • $$0.5^{o}C$$
Three rods A,B and C have the same dimensions.Their conductivities are $$K_{A}, K_{B}$$  and $$ K_{C}$$ respectively. A and B are placed end to end, with their free ends kept at certain temperature difference. C is placed separately with its ends kept at same temperature difference. The two arrangements conduct heat at the same rate $$K_{c}$$ must be equal to
  • $$K_{A}+K_{B}$$
  • $$\dfrac{K_{A}+K_{B}}{K_{A}K_{B}}$$
  • $$\dfrac{1}{2}(K_{A}+K_{B})$$
  • $$\dfrac{2K_{A}K_{B}}{K_{A}+K_{B}}$$
Three rods made of same material and having the same cross section and lengths have been joined as shown in the figure. The temperature at the junction of the rods will be :

26659_cdd62217a9ba45aba7e54cf480771d25.png
  • $$45^{o}C$$
  • $$60^{o}C$$
  • $$30^{o}C$$
  • $$20^{o}C$$
An electric kettle takes 4 A current at 220 V.
How much time will it take to boil 1 kg of water
from temperature
$$ 20^{0}C ?$$  The temperature of
boiling water is
$$ 100^{0}C ?$$
  • 12.6 min
  • 4.2min
  • 6.3 min
  • 8.4 min
A vessel contains air and saturated vapor. The pressure of air is $$\mathrm{p}_{2}$$ and $$\mathrm{p}_{1}$$ is the S.V. P. On compressing the mixture to one-fourth of its original volume, what is the increase in pressure of the mixture?
  • $$2\mathrm{p}_{1}$$
  • $$2\mathrm{p}_{2}$$
  • $$3\mathrm{p}_{1}$$
  • $$3\mathrm{p}_{2}$$
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 $$t$$ ?
  • $$\dfrac{Q}{4}$$
  • $$\dfrac{Q}{16}$$
  • $$2Q$$
  • $$\dfrac{Q}{2}$$
Three perfect gases at absolute temperatures $$\mathrm{T}_{1},\ \mathrm{T}_{2}$$ and $$\mathrm{T}_{3}$$ are mixed. The masses of molecules are $$\mathrm{m}_{1},\ \mathrm{m}_{2}$$ and $$\mathrm{m}_{3}$$ and the number of molecules are $$\mathrm{n}_{1},\ \mathrm{n}_{2}$$ and $$\mathrm{n}_{3}$$ respectively. Assuming no loss of energy, the final temperature of the mixture is:
  • $$\displaystyle \frac{(\mathrm{T}_{1}+\mathrm{T}_{2}+\mathrm{T}_{3})}{3}$$
  • $$\displaystyle \frac{\mathrm{n}_{1}\mathrm{T}_{\mathrm{l}}+\mathrm{n}_{2}\mathrm{T}_{2}+\mathrm{n}_{3}\mathrm{T}_{3}}{\mathrm{n}_{1}+\mathrm{n}_{2}+\mathrm{n}_{3}}$$
  • $$\displaystyle \frac{\mathrm{n}_{1}\mathrm{T}_{1}^{2}+\mathrm{n}_{2}\mathrm{T}_{2}^{2}+\mathrm{n}_{3}\mathrm{T}_{3}^{3}}{\mathrm{n}_{1}\mathrm{T}_{1}+\mathrm{n}_{2}\mathrm{T}_{2}+\mathrm{n}_{3}\mathrm{T}_{3}}$$
  • $$\displaystyle \frac{\mathrm{n}_{1}^{2}\mathrm{T}_{1}^{2}+\mathrm{n}_{2}^{2}\mathrm{T}_{2}^{2}+\mathrm{n}_{3}\mathrm{T}_{3}^{3}}{\mathrm{n}_{1}\mathrm{T}_{1}+\mathrm{n}_{2}\mathrm{T}_{2}+\mathrm{n}_{3}\mathrm{T}_{3}}$$
Statement-1
Radiation involves transfer of heat by electromagnetic waves.
Statement-2
Electromagnetic waves do not required any material medium for propagation.
  • Statement-1 is true, Statement-2 is true and Statement-2 is the correct explanation for Statement-1.
  • Statement-1 is true, Statement-2 is true but Statement-2 is not the correct explanation for Staement-1.
  • Statement-1 is true, Statement-2 is false.
  • Statement-1 is false, Statement-2 is true.
Consider two rods of same length and different specific heats (S$$_{1}$$, S$$_{2}$$), conductivity (K$$_{1}$$, K$$_{2}$$) and area of cross-sections (A$$_{1}$$, A$$_{2}$$) and both having temperature T$$_{1}$$ and T$$_{2}$$ at their ends. If rate of loss of heat due to conduction is equal, then:
  • $$K_{1}A_{1}=K_{2}A_{2}$$
  • $$\frac{K_{1}A_{1}}{S_{1}}=\frac{K_{2}A_{2}}{S_{2}}$$
  • $$K_{2}A_{1}=K_{1}A_{2}$$
  • $$\frac{K_{2}A_{1}}{S_{2}}=\frac{K_{1}A_{2}}{S_{1}}$$
A cylinder of radius r and thermal conductivity $$K_1$$ is surrounded by a cylindrical shell of inner radius r and outer radius 2 r, whose thermal conductivity is $$K_2$$. There is no loss of heat across cylindrical surfaces, when the ends of the combined system are maintained at temps. $$T_1$$  and  $$T_2$$. The effective thermal conductivity of the system, in the steady state is
  • $$\cfrac{{{K_1}{K_2}}}{{{K_1} + {K_2}}}$$
  • $$K_1+K_2$$
  • $$\cfrac{{{K_1} + 3{K_2}}}{4}$$
  • $$\cfrac{{3{K_1} + 3{K_2}}}{4}$$
If rc and rs respectively represents cuticular and stomatal resistance, the total resistance (R) could be expressed as
  • $$R=rc+rs$$
  • $$R=r-rs$$
  • $$\frac{1}{R}=\frac{1}{rc}+\frac{1}{rs}$$
  • $$\frac{r}{R}=\frac{1}{rc}-\frac{1}{rc}$$
$$100$$ $$\mathrm{g}$$ of water is heated from $$30^{\mathrm{o}}\mathrm{C}$$ to $$50^{\mathrm{o}}\mathrm{C}$$. Ignoring the slight expansion of the water, the change in its internal energy is (specific heat of water is $$4184$$ $$ \mathrm{J}/\mathrm{K}\mathrm{g}/\mathrm{K}$$)  
  • $$4.2$$ $$\mathrm{k}\mathrm{J}$$
  • $$8.4$$ $$\mathrm{k}\mathrm{J}$$
  • $$84$$ $$\mathrm{k}\mathrm{J}$$
  • $$2.1$$ $$\mathrm{k}\mathrm{J}$$
There are two lead spheres, the ratio c being $$1 : 2$$. If both are at the same tempe then ratio of heat contents is
  • $$1 : 1$$
  • $$1 : 2$$
  • $$1 : 4$$
  • $$1 : 8$$
Two plates of same area are placed in contact. Their thickness as well as thermal conductivities are in the ratio 2 :The outer surface of one plate is maintained at $$10^\circ C$$ and that of other at $$0^\circ C$$. What is the temp.of the common surface?
  • $$0^\circ C$$
  • $$2.5^\circ C$$
  • $$5^\circ C$$
  • $$6.5^\circ C$$
Producers gas is a mixture of
  • Carbon monoxide and nitrogen gas
  • Carbon monoxide and hydrogen gas
  • Carbon monoxide and water vapour
  • Carbon monoxide and nitrous oxide
An ideal gas can be expanded from an initial state to a certain volume through two different processes (i) $$PV^2 = constant\:and\:(ii)P = KV^2$$ where K is a positive constant. Based on the given situation, choose the correct statements
  • Final temperature in (ii) will be greater than in (i)
  • Final temperature in (ii) will be less than in (i)
  • Total heat given to the gas in case (ii) is greater than in (i)
  • Total heat given to the gas in case (ii) is less than in (i)
In a room there are four objects a wooden dish, steel dish, glass dish and a copper dish. If a fire is lit in the room so that it burns at 300 degrees centigrade, and is equidistant from all the four dishes, then after a long time the dishes can be listed in the increasing order of temperature. Which is the correct order of temperature of dishes?
  • wooden dish > steel dish > glass dish > copper dish
  • steel dish > copper dish > glass dish > wooden dish
  • copper dish > steel dish > glass dish > wooden dish
  • none of the above
At pressure P and absolute temperature T a mass M of an ideal gas fills a closed container of volume V. An additional mass 2M of the same gas is added into the container and the volume is then reduced to $$\dfrac{v}{3}$$ and the temperature to $$\dfrac{T}{3}.$$ The pressure of the gas will now be :
  • $$\dfrac{P}{3}$$
  • $$P$$
  • $$3 P$$
  • $$9 P$$
The rate of heat conduction is proportional to the cross-sectional area and temperature
gradient (temperature difference per unit length). On a typical day during the World Cup
tournament in South Africa, the air in a room is heated to $$25^{o}C$$ while the air outside is
$$-2^{o}C$$. The area of the window of the room is
$$2 m^{2}$$ and it is made of crown glass with
thickness 2 mm and thermal conductivity
$$1.0 WK^{-1}m^{-1}$$. What is the heat power loss
through the window?
  • 1.2 kW
  • 2.7 kW
  • 27 kW
  • 50 kW
Choose the correct statements from the following:
  • Good reflectors are good emitters of thermal radiations.
  • Burns caused by water at $$100^{\circ}C$$ are more severe than those caused by steam at $$100^{\circ}C$$.
  • All bodies emit thermal radiations at all temperatures greater than 0 K.
  • It is impossible to construct a heat engine of 100% efficiency.
A diatomic gas is filled inside a conducting cylinder. Now we push the piston slowly to make volume of gas half of initial. Pick correct statements
75963.png
  • Pressure of gas Increases because there is more average change in linear momentum of molecule in each collision
  • Pressure force on side wall of container increased
  • Pressure force on piston is increased
  • More molecules collide with piston per unit time
A rigid container has a hole in its wall. When the container is evacuated, its weight is 100 gm. When someair is filled in it at 27C, its weight becomes 200 gm. Now the temperature of air inside is increased by $$\Delta$$ T, the weight becomes 150 gm. $$\Delta$$ T should be :
  • $$27^{\circ}$$
  • $$\dfrac{27^{\circ}} {4}$$ C
  • $$300^{\circ}$$
  • $$327^{\circ}$$
A cuboid $$ABCDEFGH$$ is anisotropic with $$\alpha _{x}=1 \times 10^{-5} /^\circ C,\:\alpha _{y}=2 \times 10^{-5} /^\circ C,\:\alpha _{z}=3 \times 10^{-5} /^\circ C$$. Coefficient of superficial expansion of faces can be
124908.png
  • $$\beta _{ABCD}=5 \times 10^{-5}/ ^\circ C$$
  • $$\beta _{BCGH}=4 \times 10^{-5}/ ^\circ C$$
  • $$\beta _{CDEH}=3 \times 10^{-5}/ ^\circ C$$
  • $$\beta _{EFGH}=2 \times 10^{-5}/ ^\circ C$$
A vessel of volume 4 litres contains a mixture of 8 g of O$$_2$$, 14 g of N$$_2$$ and 22g of CO$$_2$$ at 27$$^o$$C. The pressure exerted by the mixture is
  • $$5 \times 10^6 N/m^2$$
  • $$6 \times 10^3 N/m^2$$
  • 10 atmosphere
  • $$7.79 \times 10^5 N/m^2$$
Sunlight contains ultraviolet radiations which makes it feel hot.
  • True
  • False
A vessel contains $$1$$ mole of O$$_2$$ (molar mass $$ 32 gm$$) at a temperature $$T$$. The pressure is $$P$$. An identical vessel containing $$1$$ mole of He (molar mass $$4 gm$$) at a temperature $$2T$$ has a pressure :
  • P
  • $$\displaystyle \frac{P}{8}$$
  • 2P
  • 8P
The temperature of the sun, if pressure is $$1.4 \times 10^9$$ atm, density is $$1.4 gcm^{-3}$$ and average molecular weight is 2, will be
$$[Given\  R = 8.4  J  mol^{-1} K^{-1}]$$
  • $$1.2 \times 10^7 K$$
  • $$2.4 \times 10^7 K$$
  • $$0.4 \times 10^7 K$$
  • $$0.2 \times 10^7 K$$
What is new gauge pressure?
  • 1.82 atm
  • 1.70 atm
  • 1.92 atm
  • none
A barometer tube 90 cm long contains some air above mercury. The reading is 74.8 cm when true atmospheric pressure is 76 cm and temperature is 30$$^o$$ C. If the reading is observed to be 75.4 cm on a day when temperature is 10$$^o$$C, then find the true pressure.
  • 76.07 cm
  • 75.6 cm
  • 76.57 cm
  • 77.123 cm
Two containers of equal volume contain the same gas at pressures $$P_1$$ and $$P_2$$ and absolute temperatures $$T_1$$ and $$T_2$$, respectively. On joining the vessels, the gas reaches a common pressure $$P$$ and common temperature $$T$$. The ratio $$\displaystyle\frac{P}{T}$$ is equal to
  • $$\displaystyle\frac{P_1}{T_1}+\frac{P_2}{T_2}$$
  • $$\displaystyle\frac{P_1T_1+P_2T_2}{{(T_1+T_2)}^2}$$
  • $$\displaystyle\frac{P_1T_2+P_2T_1}{{(T_1+T_2)}^2}$$
  • $$\displaystyle\frac{P_1}{2T_1}+\frac{P_2}{2T_2}$$
One mole of an ideal gas undergoes a process $$P = \displaystyle \frac{P_o}{1 + \left ( \displaystyle\frac{V}{V_o} \right )^2}$$, where $$P_o$$ and $$V_o$$ are constants. Find the temperature of the gas when $$V = V_o$$.
  • $$\displaystyle \frac{P_o V_o}{R}$$
  • $$\displaystyle \frac{2P_o V_o}{3R}$$
  • $$\displaystyle \frac{2 P_o V_o}{R}$$
  • $$\displaystyle \frac{P_o V_o}{2R}$$
The African bombardier beetle stenaptinus insignis can emit a jet of defensive spray from the movable tip of its abdomen. The beetle's body has reservoirs of two different chemicals. When the beetle is disturbed, these chemicals are combined in a reaction chamber producing a compounds that is warmed from $$20^o$$C to $$100^o$$C by the heat of reaction. The high pressure produced allows the compound to the sprayed out at speeds 19 ms$$^{-1}$$ scaring away predators of all kinds. Assume specific heat of two chemicals and the spray to be same as that of water $$[4.19 \times 10^3 J (kgK)^{-1}]$$ and initial temperature of chemicals to be $$20^o$$C. How many times does the pressure increase?
  • 1.5
  • 2.3
  • 1.9
  • 1.28
The correct graph between PV and P of one mol of gas at constant temperature will be
A gas is filled in a container at any temperature and at pressure 76 cm of Hg. If at the same temperature the mass of gas is increased by 50% then the resultant pressure will be
  • 38 cm of Hg
  • 76 cm of Hg
  • 114 cm of Hg
  • 152 cm of Hg
In the gas equation $$PV= RT$$, V is the volume of
  • 1 mol of gas
  • 1 g of gas
  • gas
  • 1 litre of gas
An enclosure of volume 3 litre contains 16g of oxygen, 7g of nitrogen and 11g of carbondioxide at 27$$^o$$C. The pressure exerted by the mixture is approximately
  • 9 atmosphere
  • 8.3 atmosphere
  • 3 atmosphere
  • 1 atmosphere
The pressure of a gas in a container is 10$$^{-11}$$ pascal at 27$$^o$$C. The number of molecules per unit volume of vessel will be
  • $$6 \times 10^{23} cm^{-3}$$
  • $$2.68 \times 10^{19} cm^{-3}$$
  • $$2.5 \times 10^{6} cm^{-3}$$
  • $$2400 cm^{-3}$$
Equal masses of N$$_2$$ and O$$_2$$ gases are filled in vessels A and B. The volume of vessel B is double of A. The ratio of pressure in vessel A and B will be
  • 16 : 7
  • 16 : 14
  • 32 : 7
  • 32 : 28
The dimension of universal gas constant R are
  • $$M^2 L^2 T^{-2}$$
  • $$ML^2 T^{-2} \theta^{-1}$$
  • $$M^2 L^2 T^{-2} \theta^{-2}$$
  • $$MLT^{-2} \theta^{-2}$$
In outer space there are 10 molecules per cm$$^3$$ on an average and the temperature there is 3K. The average pressure of this light gas is
  • $$10^5 Nm^{-2}$$
  • $$5 \times 10^{-14} Nm^{-2}$$
  • $$0.4 \times 10^{-16} Nm^{-2}$$
  • $$4.14 \times 10^{-16} Nm^{-2}$$
A cylinder contains 2kg of air at a pressure of 10$$^5$$Pa. If 2 kg more air is pumped into it, keeping the temperature constant, the pressure will be
  • $$10^{10} Pa$$
  • $$2 \times 10^5 Pa$$
  • $$10^5 Pa$$
  • $$0.5 \times 10^5 Pa$$
One mole of a gas at a pressure 2 Pa and temperature 27$$^o$$C is heated till both pressure and volume are doubled. What is the temperature of the gas?
  • 1200 K
  • 900 K
  • 600 K
  • 300 K
Which of the following quantities is zero on an average for the molecules of an ideal gas in equilibrium?
  • Kinetic energy
  • Momentum
  • Density
  • Speed
The temperature of water at the surface of a deep lake is $$2^{\circ}C$$. The temperature expected at the bottom is
  • $$0^{\circ}$$
  • $$2^{\circ}$$
  • $$4^{\circ}$$
  • $$-6^{\circ}$$
The pressure of a gas filled in a closed vessel increases by 0.4%. When temperature is increases by 1$$^o$$C the initial temperature of the gas is
  • 250$$^o$$C
  • 250 K
  • 250$$^o$$F
  • 2500$$^o$$C
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