JEE Questions for Physics Thermal Properties Of Matter Quiz 14 - MCQExams.com

The energy spectrum of a black body exhibits a maximum around a wavelength λ0. The temperature of the black body is now changed such that the energy is maximum around a wavelength 3λ0/4. The power radiated by the black body will now increase by a factor of
  • 256/81
  • 64/27
  • 16/9
  • 4/3
A black body at a temperature of 127oC radiates heat at the rate of 1 cal/cm2 × sec. At a temperature of 527oC the rate of heat radiation from the body in (cal/cm2 × sec) will be
  • 16.0
  • 10.45
  • 4.0
  • 2.0
The spectral energy distribution of star is maximum at twice temperature as that of sun. The total energy radiated by star is
  • Twice as that of the sun
  • Same as that of the sun
  • Sixteen times as that of the sun
  • One sixteenth of sun
A black body radiates at the rate of W watts at a temperature T. If the temperature of the body is reduced to T/3, it will radiates at the rate of (in Watts)

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    Physics-Thermal Properties of Matter-91402.png

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If the temperature of the sun were to be increased from T to 2T and its radius from R to 2R, then the ratio of the radiant energy received on the earth to what it was previously will be
  • 4
  • 16
  • 32
  • 64
The ratio of radiant energies radiated per unit surface area by two bodies is 16 : 1, the temperature of hotter body is 1000 K, then the temperature of colder body will be
  • 250 K
  • 500 K
  • 1000 K
  • 62.5 K
If the initial temperatures of metallic sphere and disc, of the mass, radius and nature are equal, then the ratio of their rate of cooling in same environment will be
  • 1 : 4
  • 4 : 1
  • 1 : 2
  • 2 : 1
When the body has the same temperature as that of surroundings
  • It does not radiate heat
  • It radiates the same quantity of heat as it absorbs
  • It radiates less quantity of heat as it receives from surroundings
  • It radiates more quantity of heat as it receives heat from surroundings
Two identical objects A and B are at temperatures TA and TB respectively. Both objects are placed in a room with perfectly absorbing walls maintained at temperatures T(TA > T > TB). The objects A and B attain temperature T eventually. Which one of the following is correct statement?
  • A only emits radiations while B only absorbs them until both attain temperature
  • A loses more radiations than it absorbs than it absorbs while B absorbs more radiations that it emits until temperature T is attained
  • Both A and B only absorbs radiations until they attain temperature T
  • Both A and B only emit radiations until they attain temperature T
A black body of surface area 10 cm2 is heated to 127oC and is suspended in a room at temperature 27oC. The initial rate of loss of heat from the body at the room temperature will be
  • 2.99 W
  • 1.89 W
  • 1.18 W
  • 0.99 W
A body of area 1 cm2 is heated to a temperature 1000 K. The amount of energy radiated by the body in 1 s is (Stefan\'s constant σ = 5.67 × 10–8 Wm–2 – K4)
  • 5.67 J
  • 0.567 J
  • 56.7 J
  • 567 J
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 plate under steady state condition is

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    Physics-Thermal Properties of Matter-91413.png

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A bucket full of hot water cools from 75oC to 70oC in time T1, from 70oC to 65oC in time T2 and from 65oC to 60oC in time T3, then
  • T1 = T2 = T3
  • T1 > T2 > T3
  • T1 < T2 < T3
  • T1 > T2 < T3
Consider two hot bodies B1 and B2 which have temperature 100oC and 80oC respectively at t = 0. The temperature of the surrounding is 40oC. The ratio of the respective rates of cooling R1 and R2 of these two bodies at t = 0 will be
  • R1 : R2 = 3 : 2
  • R1 : R2 = 5 : 4
  • R1 : R2 = 2 : 3
  • R1 : R2 = 4 : 5
Newton\'s law of cooling is a special case of
  • Stefan's law
  • Kirchhoff's law
  • Wien's law
  • Planck's law
Equal masses of two liquids are filled in two similar calorimeters. The rate of cooling will
  • Depend on the nature of the liquids
  • Depend on the specific heats of liquids
  • Be same for both the liquids
  • Depend on the mass of the liquids
Liquid is filled in a vessel which is kept in a room with temperature 20oC. When the temperature of the liquid is 80oC, then it loses heat at the rate of 60 cal/s. What will be the rate of loss of heat when the temperature of the liquid is 40oC?
  • 180 cal/s
  • 40 cal/s
  • 30 cal/s
  • 20 cal/s
Which of the following statements id true/correct?
  • During clear nights, the temperature rises steadily upward near the ground level
  • Newton's law of cooling, an approximate form of Stefan's law, is valid for natiral convection
  • The total energy emitted by a blacks body per unit time per unit area is proportional t the square of its temperature in the Kelvin scale
  • Two spheres of the same material have radii 1 m and 4 m and temperatures 4000 K and 2000 K respectively.The enrgy radiated per second by the first sphere is greater than that radiated per second by the second sphere
A cane is taken out from a refrigerator at 0oC. The atmosphere temperature is 25oC. If t1 is the time taken to heat from 0oC to 5oC and t2 is the time taken from 10oC to 15oC, then
  • t1 > t2
  • t1 < t2
  • t1 = t2
  • There is no relation
A liquid cools down from 70oC to 60oC i 5 minutes. The time taken to cool it from 60oC to 50oC will be
  • 5 minutes
  • Lesser than 5 minutes
  • Greater than 5 minutes
  • Lesser or greater than 5 minutes depending upon the density of the liquid
The rates of cooling of two different liquids put in exactly similar calorimeters and kept in identical surroundigs are the same if
  • The masses of the liquids are equal
  • Equal masses of the liquids at the same temperature are taken
  • Different volumes of the liquids at the same temperature are taken
  • Equal volumes of the liquids at the same temperature
The temperature of a liquid drops from 365 K to 361 K in 2 minutes. Find the time during which temperature of the liquid drops from 344 K to 342 K. Temperature of room is 293 K
  • 84 s
  • 72 s
  • 66 s
  • 60 s
A container contains hot water at 100oC. If in time T1 temperature falls to 80oC and in time T2 temperature falls to 60oC from 80oC, then
  • T1 = T2
  • T1 > T2
  • T1 < T2
  • None of these
Hot water kept in a beaker placed in a room cools from 70oC to 60oC in 4 minutes. The time taken by it to cool from 69oC to 59oC will be
  • The same 4 minutes
  • More than 4 minutes
  • Less than 4 minutes
  • We cannot say definitely
Newton\'s law of cooling, holds good only if the temperature difference between the body and the surroundings is
  • Less than 10oC
  • More than 10oC
  • Less than 100oC
  • More than 100oC
According to Newton\'s Law of cooling\', the rate of cooling of the body is proportional to the
  • Temperature of the body
  • Temperature of the surrounding
  • Fourth power of the temperature of the body
  • Difference of the temperature of the body and the surrounding
According to Newton\'s law of cooling, the rate of cooling of a body is proportional to (Δθ)n, where Δθ is the difference of the temperature of he body and the surrounding, and n is equal to
  • One
  • Two
  • Three
  • Four
A calorimeter of mass 0.2 kg and specific heat 900 J/kg–K. Containing 0.5 kg of a liquid of specific heat 2400 J/kg–K. Its temperature falls from 60oC to 55oC in one minute. The rate of cooling is
  • 5 J/s
  • 15 J/s
  • 100 J/s
  • 115 J/s
A hot body at temperature T losses heat to the surrounding temperature Ts by radiation. If the difference in the temperature is small then, the rate of loss of heat by the hot body is proportional to

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    Physics-Thermal Properties of Matter-91429.png

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Two rods (one semi-circular and other straight) of same material and of same cross-sectional area are joined as shown in the figure. The points A and B are maintained at different temperature. The ratio of the heat transferred through a cross-section of a semi-circular rod to the heat transferred through a cross-section of the straight rod in a given time is
Physics-Thermal Properties of Matter-91432.png
  • 2 : π
  • 1 : 2
  • π : 2
  • 3 : 2
A cylinder of radius R made of a material of thermal conductivity K1 is surrounded by a cylindrical shell of inner radius R and outer radius 2R made of material of thermal conductivity K2. The two ends of he combined system are maintained at two different temperatures. There is no loss of heat across the cylindrical surface and the system is in steady state. The effective thermal conductivity of the system is

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    Physics-Thermal Properties of Matter-91435.png

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Three rods made of the same material and having the same cross-section have been joined as shown in the figure. Each rod is of the same length. The left and right ends are kept at 0oC and 90oC respectively. The temperature of the junction of the three rods will be
Physics-Thermal Properties of Matter-91439.png
  • 45oC
  • 60oC
  • 30oC
  • 20oC
A room is maintained at 20oC by a heater of resistance 20 ohm connected to 200 volt mains. The temperature is uniform through out the room and heat is transmitted through a glass window of area 1 m2 and thickness 0.2 cm. What will be the temperature outside? Given that thermal conductivity K for glass is 0.2 cal/m/oC/sec and J = 4.2 J/cal
  • 15.24oC
  • 15.00oC
  • 24.15oC
  • None of thse
There is formation of layer of snow x cm thick on water, when the temperature of air is –θoC (less than freezing point). The thickness of layer increases from x to y in the time t, then the value of t is given by

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    Physics-Thermal Properties of Matter-91443.png

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A composite metal bar of uniform section is made up of length 25 cm of copper, 1 cm of nickel and 15 cm of aluminium. Each part being in perfect thermal contact with the adjoining part. The copper end of the composite rod is maintained at 100oC and the aluminium end at 0oC. The whole rod is covered with belt so that no heat loss occurs at the sides. If KCu = 2KAl and KAl = 3KNi, the n what will be the temperatures of Cu-Ni and Ni-Al junction respectively
  • 23.33oC and 78.8oC
  • 83.33oC and 20oC
  • 50oC and 30oC
  • 30oC and 50oC
Three rods of identical area of cross-section and made from the same metal from the sides of an isosceles triangle ABC, right angled at B. The points A and B are maintained at temperatures T and √2T respectively. In the steady state the temperature of the point C is TC. Assuming that only heat conduction takes place, TC/T is equal to
  • 2)
    Physics-Thermal Properties of Matter-91449.png

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The only possibility of heat flow in a thermos flask is through its cork which is 75 cm2 in area and 5 cm thick. Its thermal conductivity is 0.0075 cal/cm secoC. The outside temperature is 40oC and latent heat of ice is 80 cal g–1. Time taken by 500 g of ice at 0oC in the flask to melt into water at 0oC is
Physics-Thermal Properties of Matter-91453.png
  • 2.47 hr
  • 4.27 hr
  • 7.42 hr
  • 4.72 hr
A sphere, a cube and a thin circular plate, all made of the same material and having the same mass are initially heated to a temperature of 1000oC. Which one of these will cool first
  • Plate
  • Sphere
  • Cube
  • None of these
Two identical conductance rods are first connected identically to two vessels, one containing water at 100oC and the other containing ice at 0oC. In he second case, the rods are joined end to end and connected to the same vessels. Let q1 and q2 g/s be the rate of melting of ice in two cases respectively. The ratio of q1/q2 is
  • 1/2
  • 2/1
  • 4/1
  • 1/4
A black body is at a temperature of 2880 K. The energy of radiation emitted by this object with wavelength between 499 nm and 500 nm is U1, between 999 nm and 1000 nm is U2 and between 1499 nm and 1500 nm is U3. The Wien\'s constant b = 2.88 × 106 nmK. Then,
  • U1 = 0
  • U3 = 0
  • U1 > U2
  • U2 > U1
A black metal foil is warmed by radiation from a small sphere at temperature T and at a distance d. It is found that the power received by the foil is \'P\'. If both the temperature and the distance are doubled, the power received by the foil will be
  • 16P
  • 4P
  • 2P
  • P
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 then which of the following options is correct?
Physics-Thermal Properties of Matter-91459.png

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    Physics-Thermal Properties of Matter-91461.png

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Two metallic spheres S1 and S2 are made of the same material and have identical surface finish. The mass of S2 is three times that of S1. Both the spheres are heated to the same high temperature and placed in the same room having lower temperature but are thermally insulated from each other. The ration of the initial rate of cooling of S1 to that of S2

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  • 2)
    Physics-Thermal Properties of Matter-91466.png

  • Physics-Thermal Properties of Matter-91467.png

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Three discs A, B and C having radii 2 m, 4 m and 6 m respectively are coated with carbon black on their other surfaces. The wavelengths corresponding to maximum intensity are 300 nm, 400 nm and 500 nm respectively. The power radiated by them are Qa, Qb and Qc resectively
  • Qa is maximum
  • Qb is maximum
  • Qc is maximum
  • Qa = Qb = Qc
The total energy radiated from a black body source is collected for one minute and is used to heat a quantity of water. The temperature of water id found to increase form 20oC to 20.5oC. If the absolute temperature of the black body is doubled and the experiment is repeated with the same quantity of water at 20oC, the temperature of water will be
  • 21oC
  • 22oC
  • 24oC
  • 28oC
A solid sphere and a hollow sphere of the same material and size are heated to the same temperature and allowed t col in the same surroundings. If the temperature difference between each sphere and its surroundings is T, then
  • The hollow sphere will cool at a faster rate for all values of T
  • The solid sphere will cool at a faster rate for all values of T
  • Both spheres will cool at the same rate for all values of T
  • Both spheres will cool at the same rate only for small values of T
A solid copper cube of edges 1 cm is suspended in an evacuated enclosure. Its temperature is found to fall from 100oC to 99oC 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 100oC to 99oC will be approximately
  • 25 s
  • 50 s
  • 200 s
  • 400 s
A body initially at 80oC cools to 64oC in 5 minutes and to 52oC in 10 minutes. The temperature of the body after 15 minutes will be
  • 42.7oC
  • 35oC
  • 47oC
  • 40oC
A 5 cm thick ice block is there on the surface of water in a lake. The temperature of air is –10oC; how much time it will take to double the thickness of the block?
(L = 80 cal/g, Kice = 0.004 erg/s-k, dice = 0.92 g cm–3)
  • 1 hr
  • 191 hr
  • 19.1 hr
  • 1.91 hr
A cylindrical rod with one end in a steam chamber and the other end in ice results in melting of 0.1 g of ice per second. If the rod is replaced by another with half the length and double the radius of the first and if the thermal conductivity of material of second rod is 1/4 that of first, the rate at which ice melts in g/s will be
  • 3.2
  • 1.6
  • 0.2
  • 0.1
0:0:1


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