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NCERT Solutions for class 11 Physics | Chapter 11 - Thermal Properties of Matter

(1) A glass full of hot milk is poured on the table. It begins to cool gradually. Which of the following is correct?
[A] the rate of cooling is constant till milk attains the temperature of the surrounding
[B] the temperature of milk falls off exponentially with time
[C] while cooling, there is a flow of heat from milk to the surrounding as well as from surrounding to the milk but the net flow of heat is from milk to the surrounding and that is why it cools
[D] all three phenomena, conduction, convection, and radiation are responsible for the loss of heat from milk to the surroundings
Answer: B, C, D
(2) Refer to the plot of temperature versus time showing the changes in the state of ice on heating. Which of the following is correct?

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[A] the region AB represents ice and water in thermal equilibrium
[B] at B water starts boiling
[C] at C all the water gets converted into steam
[D] C to D represents water and steam in equilibrium at boiling point
Answer: A, D

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(3) ‘Gulab Jamuns’ (assumed to be spherical) are to be heated in an oven. They are available in two sizes, one twice bigger than the other. Pizzas (assumed to be discs) are also to be heated in the oven. They are also in two sizes, one twice big in radius than the other. All four are put together to be heated to oven temperature. Choose the correct option from the following:
[A] both size gulab jamuns will get heated at the same time
[B] smaller gulab jamuns are heated before bigger ones
[C] smaller pizzas are heated before bigger ones
[D] bigger pizzas are heated before smaller ones
Answer: B, C
(4) Mark the correct options:
[A] A system X is in thermal equilibrium with Y but not with Z. System Y and Z may be in thermal equilibrium with each other
[B] A system X is in thermal equilibrium with Y but not with Z. Systems Y and Z are not in thermal equilibrium with each other
[C] A system X is neither in thermal equilibrium with Y nor with Z. The systems Y and Z must be in thermal equilibrium with each other
[D] A system X is neither in thermal equilibrium with Y nor with Z. The system Y and Z may be in thermal equilibrium with each other
Answer: B, D
(5) A sphere, a cube, and a thin circular plate, all of the same material and same mass are initially heated to same high temperature.
[A] plate will cool fastest and cube the slowest
[B] sphere will cool fastest and cube the slowest
[C] plate will cool fastest and sphere the slowest
[D] cube will cool fastest and plate the slowest
Answer: plate will cool fastest and sphere the slowest
(6) 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: kinetic energy of random motion of molecules
(7) As the temperature is increased, the time 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 of the centre of mass below the centre of the bob
[D] decreases as its effective length remains the same but the centre of mass shifts above the centre of the bob
Answer: increases as its effective length increases even though its centre of mass still remains at the centre of the bob
(8) An aluminium sphere is dipped into water. Which of the following is true?
[A] buoyancy will be less in water at 0oC than that in water at 4°C
[B] buoyancy will be more in the water at 0oC than that in water at 4°C
[C] buoyancy in water at 0oC will be same as that in the water at 4°C
[D] buoyancy may be more or less in water at 4oC depending on the radius of the sphere
Answer: buoyancy will be less in water at 0oC than that in water at 4°C
(9) 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 increases
[B] its speed of rotation decreases
[C] its speed of rotation remains the same
[D] its speed increases because its moment of inertia increases
Answer: its speed of rotation decreases
(10) A bimetallic strip is made of aluminium and steel (αAl > αsteel). On heating, the strip will
[A] remain straight
[B] get twisted
[C] will bend with aluminium on the concave side
[D] will bend with steel on the concave side
Answer: will bend with steel on the concave side
(11) The sprinkling of water reduces the temperature of the closed room
[A] The water has large latent heat of vaporization
[B] Water is bad conductor of heat
[C] Specific heat of water is high
[D] the temperature of water is less than that of room
Answer: The water has large latent heat of vaporization
(12) Which of the following devices is used to detect thermal radiation?
[A] Thermopile
[B] Constant volume air thermometer
[C] Liquid thermometer
[D] Six Maximum and minimum thermometer
Answer: Thermopile
(13) the coefficient of linear expansion of an in homogeneous rod changes linearly from α1to α2from one end to the other end of the rod. The effective coefficient of linear expansion of the rod is
[A] α12
[B] 1/2(α12)
[C] √α1α2
[D] None of the these
Answer: 1/2(α12)
(14) If a is coefficient of Linear expansion, b coefficient of areal expansion, c coefficient of Volume expansion. Which of the following is true
[A] b=2a
[B] c=3a
[C] b=3a
[D] a=2b
Answer: A, B
(15) An Aluminium Rod of length L0rest on a smooth horizontal base if the temperature is increase by ΔT °C. What will be the longitudinal strain developed
[A] αΔT
[B] Zero
[C] -αΔT
[D] none of the above
Answer: Zero
(16) 10 litres of benzene weight
[A] more in summer than in winter
[B] more in winter than in Summer
[C] equal in winter and summer
[D] none of above
Answer: more in winter than in Summer
(17) A constant volume air thermometer works on
[A] Pascal law
[B] Charles law
[C] Boyles law
[D] Archimedes
Answer: Charles law
(18) For any material, density ρ , mass m and volume V are related by ρ = m/V and B is coefficient of volume expansion then which one is true
[A] B = (1/ρ) (dρ/ dT)
[B] B = -(1/ρ) (dρ/ dT)
[C] B = (1/ρ) (dρ/ dV)
[D] B = (1/ρ) (dρ/ dV)
Answer: B = -(1/ρ) (dρ/ dT)
(19) if α is the Coefficient of linear expansion of block and L denotes length, T denotes Temperature then which one of these is true
[A] dL - α L dT = 0
[B] dL + α L dT = 0
[C] αdL - L dT = 0
[D] αdL - +L dT = 0
Answer: dL - α L dT = 0
(20) A sphere of mass m and diameter D is Heated by temperature ΔT , if Coefficient of linear expansion is α what will be the change in the Surface Area
[A] π D2α ΔT (α ΔT+ 2)
[B] π D2α ΔT (α ΔT- 2)
[C] π D2α ΔT (α ΔT+ 4)
[D] π D2α ΔT (α Δ- 4)
Answer: π D2α ΔT (α ΔT+ 2)

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