JEE Questions for Physics Thermal Properties Of Matter Quiz 2 - MCQExams.com

Three rods of same dimensions are arranged as shown in figure, they have thermal conductivities K1 , K2 and K3. The points P and Q are maintained at different temperatures for the heat to flow at the same rate along PRQ and PQ.
Physics-Thermal Properties of Matter-90720.png

  • Physics-Thermal Properties of Matter-90721.png
  • 2)
    Physics-Thermal Properties of Matter-90722.png

  • Physics-Thermal Properties of Matter-90723.png

  • Physics-Thermal Properties of Matter-90724.png
A, B and C are three identical conductors but made from different materials. They are kept in contact as shown. Their thermal conductivites are k, 2k and k/2. The fee and of A is at 100oC and the free end of C is 0oC. During steady state, the temperature of the junction of A and B is nearly
Physics-Thermal Properties of Matter-90725.png
  • 37°C
  • 71°C
  • 29°C
  • 63°C
An ideal black body at room temperature is thrown into a furnance. It is observed that
  • it is the darkest body at all times
  • it cannot be distinguished at all times
  • initially it is the darkest body and later it becomes brightest
  • initially it is the darkest body and later it cannot be distinguished
A composite block is made of slabs A, B, C, D and E of different thermal conductivities (given in terms of a constant K) and sizes (given in terms of length L) as shown in the figure. All slabs are of same width. Heat Q flows only from left to right through the blocks. Then, in steady state
Physics-Thermal Properties of Matter-90726.png
  • (a) heat flow through A and E slabs are same
  • (b) heat flow through slab E is maximum
  • (c) temperature difference across slab E is smallest
  • (d) heat flow through C = heat flow through B + heat flow through D
Three identical rods A, B and C are placed end to end. A temperature difference is maintained between the free ends of A and C. The thermal conductivity of B is thrice that of C and half of that of A. The effective thermal conductivity of the system will be (KA is the thermal conductivity of rod A)

  • Physics-Thermal Properties of Matter-90727.png
  • 2)
    Physics-Thermal Properties of Matter-90728.png

  • Physics-Thermal Properties of Matter-90729.png

  • Physics-Thermal Properties of Matter-90730.png
1.56 × 105 J of heat is conducted through is 2 m2 wall of 12 cm thick in one hour. Temperature difference between the two sides of the wall is 20°C. The thermal conductivity of the material of the wall is (in Wm-1 K-1)
  • 0.11
  • 0.13
  • 0.15
  • 1.2
A long metallic bar is carrying heat from one of its ends to the other end under steady-state.The variation of temperature 0 along the length x of the bar from its hot end is best described by which of the following figure?

  • Physics-Thermal Properties of Matter-90731.png
  • 2)
    Physics-Thermal Properties of Matter-90732.png

  • Physics-Thermal Properties of Matter-90733.png

  • Physics-Thermal Properties of Matter-90734.png
Two rods of equal lengths and areas of cross-section are kept parallel and hanged between temperatures 20°C and 80°C.The ratio of the effective thermal conductivity to that of the first rod is
Physics-Thermal Properties of Matter-90735.png
  • 7 : 4
  • 7 : 6
  • 4 : 7
  • 7 : 8
For an opaque body, coefficient of transmission is
  • zero
  • 1
  • 0.5
  • ∞
Two rods of the same length and diameter having thermal conductivities K1 and K2 are joined in parallel. The equivalent thermal conductivity of the combination is

  • Physics-Thermal Properties of Matter-90736.png
  • 2)
    Physics-Thermal Properties of Matter-90737.png

  • Physics-Thermal Properties of Matter-90738.png

  • Physics-Thermal Properties of Matter-90739.png
Two slabs A and B of equal surface area are placed one over the other such that their surfaces are completely in contact. The thickness of slab A is twice that of B. The coefficient of thermal conductivity of slab A is twice that of B. The first surface of slab A is maintained at 100°C, while the second surface of slab B is maintained at 25°C. The temperature at the contact of their surfaces is
  • 62.5° C
  • 45° C
  • 55° C
  • 85° C
Which of the following circular rods (given radius r and length I), each made of the same material as whose ends are maintained at the same temperature will conduct most heat?
  • r = 2r0, l = 2l0
  • r = 2r0, l = l0
  • r = r0, l = l0
  • r = r0, l = 2l0
The end A of a rod AB of length 1 m is maintained at 100°C and the end B at 10°C. The temperature at a distance of 60 cm from the end B is
  • 64° C
  • 36° C
  • 46° C
  • 72° C
The coefficient of thermal conductivity of copper is 9 times that of steel. In the composite cylindrical bar shown in the figure, what will be the temperature at the junction of copper and steel?
Physics-Thermal Properties of Matter-90740.png
  • 75° C
  • 67° C
  • 25° C
  • 33° C
Three rods made of same material and having same cross-section are joined as shown in the figure. Each rod is of same length. The temperature at the junction of the three rods is
Physics-Thermal Properties of Matter-90742.png
  • 45° C
  • 90° C
  • 30° C
  • 20° C
  • 60° C
A conductor of area of cross-section 100 cm2 and length 1 cm has coefficient of thermal conductivity 0.76 cal s -1m -1K -1. If 30 cal of heat flows through the conductor per second. Find the temperature difference across the conductor.
  • 40° C
  • 20° C
  • 25° C
  • 35° C
The thermal conductivity of a rod is 2. What is its thermal resistivity?
  • 0.5
  • 1
  • 0.25
  • 2
Which one of the following processes depends on gravity?
  • conduction
  • convection
  • radiation
  • None of these
An ice box made of Styrofoam (thermal conductivity = 0.01 Jm-1 s -1 K-1) is used to keep liquids cool. It has a total wall area including lid of 0.8 m 2 and wall thickness of 2.0 cm. A bottle of water is placed in the box and filled with ice. If the outside temperature is 30°C, the rate of flow of heat into the box is (in Js-1)
  • 16
  • 14
  • 12
  • 10
Consider a compound slab consisting of two different materials having equal lengths, thicknesses and thermal conductivities K and 2K respectively. The equivalent thermal conductivity of the slab is

  • Physics-Thermal Properties of Matter-90744.png
  • 2)
    Physics-Thermal Properties of Matter-90745.png

  • Physics-Thermal Properties of Matter-90746.png

  • Physics-Thermal Properties of Matter-90747.png
One end of a metal rod of length 1.0 m and area of cross-section 100 cm2 is maintained at 100°C.If the other end of the rod is maintained at 0°C, the quantity of heat transmitted through the rod per minute is (coefficient of thermal conductivity of material of rod = 100 W/m-K)
  • 3 × 103 J
  • 6 × 103 J
  • 9 × 103 J
  • 12 × 103 J
Consider a black body radiation in a cubical box at absolute temperature T. If the length of each side of the box is doubled and the temperature of the walls of the box and that of the radiation is halved, then the total energy
  • halves
  • doubles
  • quadruples
  • remains constant
Two spherical black bodies of radii r1 and r2 and with surface temperatures T1 and T2 respectively radiate the same power. Then, the ratio of r1 and r2 will be

  • Physics-Thermal Properties of Matter-90749.png
  • 2)
    Physics-Thermal Properties of Matter-90750.png

  • Physics-Thermal Properties of Matter-90751.png

  • Physics-Thermal Properties of Matter-90752.png
The temperatures of two bodies A and B are respectively 727°C and 327°C. The ratio HA : HB of the rates of heat radiated by them is
  • 727 : 327
  • 5 : 3
  • 25 : 9
  • 625 : 81
Three very large plates of same area are kept parallel and close to each other. They are considered as ideal black surfaces and have very high thermal conductivity. The first and third plates are maintained at temperatures 2T and 3T respectively. The temperature of the middle (i.e. second ) plate under steady state condition, is

  • Physics-Thermal Properties of Matter-90753.png
  • 2)
    Physics-Thermal Properties of Matter-90754.png

  • Physics-Thermal Properties of Matter-90755.png

  • Physics-Thermal Properties of Matter-90756.png
Two spheres of radii 8 cm and 2 cm are cooling. Their temperatures are 127°C and 527°C respectively. Find the ratio of energy radiated by them in the same time
  • 0.06
  • 0.5
  • 1
  • 2
'Good emitters are good absorbers' is a statement concluded from
  • Newton's law of cooling
  • Stefan's law of radiation
  • Provost's theory
  • Kirchoff's law
A black body at a temperature of 227°C radiates heat at the rate of 5 cal cm-2s -1. At a temperature of 727°C, the rate of heat radiated per unit area in cal cm 2s-1 is
  • 400
  • 80
  • 40
  • 15
The wavelength X. = 5.5 × 10-7m when temperature of the sun is 5500 K. If the furnace has wavelength λm equal to 1 is 10-7m, then temperature of furnace is
  • 5000 K
  • 1750 K
  • 3750 K
  • 2750 K
We consider the radiation emitted by the human body. Which of the following statement is true?
  • The radiation is emitted during the summers and absorbed during the winters
  • The radiation emitted lies in the ultraviolet region and hence is not visible
  • The radiation emitted is in the infrared region
  • The radiation is emitted only during the day
The temperature at which a black body ceases to radiate energy, is
  • zero
  • 273 K
  • 30 K
  • 100 K
Three objects coloured black, grey and white can with stand hostile conditions at 2800°C. These objects are thrown into furnace where each of them attains a temperature of 2000°C. Which object will glow brightest?
  • The white object
  • The black object
  • All glow with equal brightness
  • Grey object
A perfect black body is one whose emissive power is
  • maximum
  • zero
  • unity
  • minimum
2 L of water at initial temperature of 27°C is heated by a heater of power 1 kW. If the lid of kettle is opened, then heat is lost at the constant rate of 160 J/s. Find the time required to raise the temperature of water to 77°C with the lid open (specific heat of water 4.2 kJ/kg).
  • 5 min 40 s
  • 14 min 20 s
  • 8 min 20 s
  • 16 min 10 s
Same quantity of ice is filled in each of the two metal containers P and Q having the same size, shape and wall thickness but made of different materials. The containers are kept in identical surroundings. The ice in P melts completely in time t1 whereas in Q takes a time t2. The ratio of thermal conductivities of the materials of P and Q is
  • t2 : t1
  • t1 : t2
  • t12 : t22
  • t22 : t12
A very small hole in an electric furnace is used for heating metals. The hole nearly acts as a black body. The area of the hole is 200 mm2. To keep a metal at 727°C, heat energy flowing through this hole per sec, in joules is (σ = 5.67 × 10-8Wm-2K-4 )
  • 22.68
  • 2.268
  • 1.134
  • 11.34
A cane is taken out from a refrigerator at 0°C. The atmospheric temperature is 25°C. If t1 is the time taken to heat from 0°C to 5°C and t2 is the time taken from 10°C to 15°C, then
  • t1 > t2
  • t1 < t2
  • t1 = t2
  • there is no relation
A body cools down from 65°C to 60°C in 5 min. It will cool down from 60°C to 55°C in
  • 5 min
  • less than 5 min
  • more than 5 min
  • less than or more than 5 min depending on whether its mass is more than or less than 2 kg
Hot food cools from 94°C to 86°C in 2 min when the room temperature is 20°C. How long would the food take to cool from 71°C to 69°C?
  • 12 s
  • 25 s
  • 16 s
  • 42 s
The quantities of heat required to raise the temperatures of two copper spheres of radii r1 and r2 (r1 =1.5 r2 ) through 1 K are in the ratio of
  • 1
  • 2)
    Physics-Thermal Properties of Matter-90759.png

  • Physics-Thermal Properties of Matter-90760.png

  • Physics-Thermal Properties of Matter-90761.png
Two spherical bodies A (radius 6 cm) and B (radius 18 cm) are at temperatures T1 and T2 respectively. The maximum intensity in the emission spectrum of A is at 500 nm and in that of B is at 1500 nm. Considering them to be black bodies, what will be the ratio of the rate of total energy radiated by A to that of B?
  • 9
  • 9.5
  • 8
  • 8.5
Temperatures of two stars are in ratio 3:2.If wavelength of maximum intensity of first body is 4000 A°, what is corresponding wavelength of second body?
  • 9000 A°
  • 6000 A°
  • 2000 A°
  • 8000 A°
The luminosity of the Rigel star is 17000 times that of the sun. Assume both to be perfectly black bodies. If the surface temperature of the sun is 6000 K, then the temperature of the star is
  • 68400 K
  • 1.02 × 108 K
  • 12000 K
  • 68400° C
Hot water cools from 60°C to 50°C in the first 10 min and to 42°C in the next 10 min. Then, the temperature of the surroundings is
  • 20° C
  • 30° C
  • 15° C
  • 10° C
In a radiation spectrum obtained from a furnace of 2600 K has maximum intensity at 12000 A wavelength. If the maximum intensity in spectrum of a star is at 5000 A then the temperature of the outer surface of star is
  • 7800 K
  • 6240 K
  • 5240 K
  • 3640 K
A body initially at 80°C cools to 64°C in 5 min and to 52°C in 10 min.The temperature of the surrounding is
  • 26° C
  • 16° C
  • 36° C
  • 40° C
The amount of heat energy radiated by a metal at temperature T is E . When the temperature is increased to 3 T , energy radiated is
  • 81 E
  • 9 E
  • 3 E
  • 27 E
The surface temperature of the stars is determined using
  • Planck's law
  • Wien's displacement law
  • rayleigh - Jeans law
  • Kirchoff's law
According to Newton's law of cooling, the rate of cooling is proportional to (∆θ) , where ∆θ is the temperature difference between the body and the surroundings and n is equal to
  • 3
  • 2
  • 1
  • 4
Two spheres P and Q, of same colour having radii 8 cm and 2 cm are maintained at temperatures 127°C and 527°C respectively. The energy radiated by P and Q is
  • 0.054
  • 0.0034
  • 1
  • 2
0:0:1


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