THERMAL EXPANSION, CALORIMETRY \& HEAT TRANSFER EXERCISE-3  [REASONING TYPE]

THERMAL EXPANSION \& CALORIMETRY

(A) Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

(B) Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.

(C) Assertion is true but the Reason is false

(D) Assertion and Reason both are false

Q.1 Assertion: The transfer of energy from a hot body to a cold body is a non-mechanical process.

Reason : When two bodies, one hot and other cold are kept in thermal contact, then internal energy of hot body decreases while that of cold body increases.

(1) A

(2) \(B\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.2 Assertion : In summers length of metallic scale will increase.

Reason : In summers a metallic scale will read more than the actual.

(1) A

(2) B

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.3 Assertion : A metallic rod is fixed from two ends as shown in figure. When the temperature is increased compressive stresses are developed in the rod.

Reason : At higher temperature, natural length of the rod will be more.

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.4 Assertion : Water vapours at \(100^{\circ} \mathrm{C}\) will burn you more than water at \(100^{\circ} \mathrm{C}\).

Reason : Heat requiredto convert total mass of any substance from one state to another state is called latent heat.

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) D

Q.5 Assertion : Good conductors of electricity are also good conductors of heat.

Reason : In good conductors of electricity there are large numbers of free elecrons.

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.6 Assertion : The molecules at \(0^{\circ} \mathrm{C}\) ice and \(0^{\circ} \mathrm{C}\) water will have same potential energy.

Reason : Potential energy depends only on temperature of the system.

(1) A

(2) \(B\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.7 Assertion : Two bodies at different temperatures, if brought in thermal contact do not necessary settle to the mean temperature.

Reason : The two bodies may have different thermal capacities.

(1) A

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.8 Assertion : Gas thermometers are more sensitive than liquid thermometers

Reason : Coefficent of thermal expansion of gases is more then liquid.

(1) \(\mathrm{A}\)

(2) \(B\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\) 

THERMAL EXPANSION, CALORIMETRY \& HEAT TRANSFER

Q.9 Assertion : Water is considered unsuitable for use in thermometers

Reason : This is due to small specific heat and high thermal conductivity.

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.10 Assertion : When water is heated by a burner in metallic container its level first decreases then increases.

Reason : Thermal conductivity of metal is very large compared to water.

(1) A

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.11 Assertion : Fahrenheit is the smallest unit measuring temperature.

Reason : Fahrenheit was the first temperature scale used for measuring temperature

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) D

Q.12 Assertion : Specific heat capacity is the cause of formation of land and sea breeze.

Reason : The specific heat of water is more than land.

(1) A

(2) B

(3) \(\mathrm{C}\)

(4) D

HEAT TRANSFER

Q.13 Assertion : For higher temperature, the peak emission wavelength of a black body shifts to lower wavelengths.

Reason : Peak emission wavelength of a blackbody is proportional to the fourth power of temperature.

(1) \(\mathrm{A}\)

(2) \(B\)

(3) \(\mathrm{C}\)

(4) D

Q.14 Assertion : Snow is better insulator than ice.

Reason : Snow contain air packet and air is good insulator of heat.

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.15 Assertion : All black coloured objects are considered black bodies.

Reason : Black colour is a good reflector of heat.

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) D

Q.16 Assertion : Gravity plays very important role in the process of natural convection.

Reason : Convection mainly takes place in liquids and gases.

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) D

Q.17 Assertion : A brass tumbler feels much colder than a wooden tray on a chilly day.

Reason: The thermal conductivity of brass is less than that of wood.

(1) A

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.18 Assertion : Animals curl into a ball, when they feel very cold.

Reason : Animals by curling their body reduce the surface area.

(1) \(\mathrm{A}\)

(2) B

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.19 Assertion : Like light radiations, thermal radiations are also electromagnetic radiation. Reason : The thermal rediations require no medium for propagation.

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\) 

THERMAL EXPANSION, CALORIMETRY \& HEAT TRANSFER

Q.20 Assertion : A beaker is completely filled with water at \(4^{\circ} \mathrm{C}\). It will overflow, both when heated for cooled.

Reason : There is expansion of water below and above \(4^{\circ} \mathrm{C}\).

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.21 Assertion : As the temperature of the blackbody increases, the wavelength at which the spectral intensity \(\left(\mathrm{E}_{\lambda}\right)\) is maximum, decreases.

Reason : The wavelength at which the spectral intensity will be maximum for a black body is proportional to the fourth power of its absolute temperature.

(1) A

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.22 Assertion : If temperature of any IBB (Ideal Black Body) is increased by \(100 \%\) then there will be \(400 \%\) increase in quantity of radiation emitted from its surface.

Reason : Equation \(\frac{\Delta \mathrm{E}}{\mathrm{E}}=4 \frac{\Delta \mathrm{T}}{\mathrm{T}}\) also true for large percentage increase \(\left(\mathrm{E}=\sigma \mathrm{T}^{4}\right)\)

(1) A

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) D

Q.23 Assertion : Wein's displacement law fails at short wavelengths.

Reason : Intensity of radiations of very short wavelength is small.

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.24 Assertion : In the conduction made of transmission of heat, transfer of heat is due to interatomic collisions, without the atoms leaving their locations.

Reason : Steady state during conduction of heat through a rod means temperature gradient of all parts of the rod is same.

(1) \(\mathrm{A}\)

\((2) \mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.25 Assertion : In a room containing air, heat can go from one place to another by radiation only.

Reason : In conduction and convection, heat is transferred from one place to other by actual motion of heated material.

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) D

Q.26 Assertion : A hollow metallic closed container maintained at a uniform temperature can act as a source of black body radiation.

Reason : All metals act as black bodies.

(1) \(\mathrm{A}\)

(2) B

(3) \(\mathrm{C}\)

(4) D

Q.27 Assertion : As the temperature of a black body is raised, wavelength corresponding to which energy emitted is maximum, reduces.

Reason : Higher temperature would mean higher energy and hence higher wavelength.

(1) A

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) D

Q.28 Assertion : Radiation is the fastest mode of heat transfer.

Reason : The nature of emitted radiations from ideal black body depends only on its temperature.

(1) \(\mathrm{A}\)

\((2) \mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.29 Assertion : Heat radiation are always obtained in infrared region of electromagnetic wave spectrum Reason : Complementary colour are those two colour present in the spectrum which when mixed produce white light.

(1) \(\mathrm{A}\)

\((2) \mathrm{B}\)

(3) \(\mathrm{C}\)

(4) D 

THERMAL EXPANSION, CALORIMETRY \& HEAT TRANSFER

Q.30 Assertion : Heat radiations and light have identical properties.

Reason : A cool body does not radiate heat to the hotter surrroundings.

(1) \(\mathrm{A}\)

\((2) \mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.31 Assertion : Coolness is felt in summer when we enter in air conditioned room.

Reason : At very possible temperature there is a continuous heat energy exchange between a body and its surrounding.

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) D

Q.32 Assertion : IBB (Ideal Black Body) is a good emitter at high temperature.

Reason : Good emitters are good absorbers and vice versa.

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.33 Assertion : Absorptive power is a dimensionless quantitiy and a body having low emissive power should have low absorptive power.

Reason : The ratio of emissive power to absorptive power is same for all bodies at a given temperature and is equal to the emissive power of a black body at that temperature.

(1) A

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.34 Assertion : Abody with large reflectivity is a poor emitter.

Reason : A body with large reflectivity is a poor absorber of heat.

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) D

Q.35 Assertion : A body that is a good radiator is also a good absorber of radiation at a given wavelength. Reason : According to Kirchoff's law the absorptivity of a body is equal to its emissivity at a given wavelength.

(1) \(\mathrm{A}\)

(2) \(B\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.36 Assertion : For higher temperature the peak emission wavelength of a black body shift to lower wavelength.

Reason : Peak emission wavelength of black body is proportional to the fourth power of temperature.

(1) \(\mathrm{A}\)

\((2) \mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.37 Assertion : Perspiration from human body helps in cooling the body.

Reason : A thin layer of water on the skin enhances its emissivity.

(1) \(\mathrm{A}\)

\((2) \mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.38 Assertion : Bodies radiate heat at all temperature.

Reason : Rate of radiation of heat is inversely proportional to the fourth power of absolute temperature.

(1) A

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\)

Q.39 Assertion : Blue star is at high temperature that red star.

Reason : Wien's displacement law states that \(\mathrm{T} \alpha \frac{1}{\lambda_{\mathrm{m}}}\).

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) D

Q.40 Assertion : If the temperature of a star is doubled, then the rate of loss of heat from it become 16 times. Reason : Specific heat varies with temperature.

(1) \(\mathrm{A}\)

(2) \(\mathrm{B}\)

(3) \(\mathrm{C}\)

(4) D

Q.41 Assertion : The radiation from sun's surface varies as the fourth power of its absolute temperature. Reason : The sun is not a black body.

(1) A

\((2) \mathrm{B}\)

(3) \(\mathrm{C}\)

(4) \(\mathrm{D}\) 

EXERCISE-4

SECTION-A : Previous Year's Questions  THERMALEXPANSION & CALORIMETRY

Q.1 Water is used to cool radiators of engines, because

(1) Of its lower density

(2) It is easily available

(3) It is cheap

(4) It has high specific heat

[AFMC 1998]

Q.2 The SI unit of mechanical equivalent of heat is -

(1) joule \(\times\) calorie

(2) joule/calorie

(3) calorie \(\times\) erg

(4) \(\mathrm{erg} /\) calorie

[MP PMT/PET-1998]

Q.3 The coefficients of linear expansions of brass and steel are \(\alpha_{1}\) and \(\alpha_{2}\) respectively. When we take a brass rod of length \(\ell_{1}\) and a steel rod of length \(\ell_{2}\) at \(0^{\circ} \mathrm{C}\), then the difference in their lengths \(\left(\ell_{2}-\ell_{1}\right)\) will remain the same at all temperatures if:

(1) \(\alpha_{1} \ell_{1}=\alpha_{2} \ell_{2}\)

(2) \(\alpha_{1} \ell_{2}=\alpha_{2} \ell_{1}\)

(3) \(\alpha_{1}^{2} \ell_{2}=\alpha_{2}^{2} \ell_{1}\)

(4) \(\alpha_{1} \ell_{2}^{2}=\alpha_{2} \ell_{1}^{2}\)

[AIPMT 1999]

Q.4 The amount of heat required to convert gram of ice at \(0^{\circ} \mathrm{C}\) into steam at \(100^{\circ} \mathrm{C}\) will be -

[RPMT-1999]

(1) \(716 \mathrm{cal}\)

(2) \(500 \mathrm{cal}\)

(3) \(180 \mathrm{cal}\)

(4) \(100 \mathrm{cal}\)

Q.5 10 grams of ice at \(0^{\circ} \mathrm{C}\) is mixed with 10 grams of water at \(20^{\circ} \mathrm{C}\). The final temperature of mixture will be-

[RPMT-1999]

(1) \(50^{\circ} \mathrm{C}\)

(2) \(10^{\circ} \mathrm{C}\)

(3) \(0^{\circ} \mathrm{C}\)

(4) \(15^{\circ} \mathrm{C}\)

Q.6 Value of \(-40^{\circ} \mathrm{C}\) in Fahrenheit scale is :

(1) \(-40^{\circ} \mathrm{F}\)

(2) \(32^{\circ} \mathrm{F}\)

(3) \(-32^{\circ} \mathrm{F}\)

(4) \(40^{\circ} \mathrm{C}\)

[RPMT 1999]

Q.7 The amount of heat required to change \(1 \mathrm{gm}\left(0^{\circ} \mathrm{C}\right)\) of ice into water of \(100^{\circ} \mathrm{C}\), is : [RPMT 1999]

(1) \(716 \mathrm{cal}\)

(2) \(500 \mathrm{cal}\)

(3) \(180 \mathrm{cal}\)

(4) \(100 \mathrm{cal}\)

Q.8 If temperature of an object is \(140^{\circ} \mathrm{F}\), then its temperature in centrigrade is :

[RPMT 1999]

(1) \(105^{\circ} \mathrm{C}\)

(2) \(32^{\circ} \mathrm{C}\)

(3) \(140^{\circ} \mathrm{C}\)

(4) \(60^{\circ} \mathrm{C}\)

Q.9 Latent heat of \(1 \mathrm{gm}\) of steam is \(536 \mathrm{cal} / \mathrm{gm}\), then its value in joule \(/ \mathrm{kg}\) is:

[RPMT 1999]

(1) \(2.25 \times 10^{6}\)

(2) \(2.25 \times 10^{3}\)

(3) \(2.25\)

(4) none of these

Q.10 At \(100^{\circ} \mathrm{C}\), the substance that causes the causes the most severe burn, is -

(1) Oil

(2) Steam

(3) Water

(4) Hot air

[Karnataka CET (Engg. /Med.) 1993; UPSEAT-1999]

Q.11 Calorimeters are made of which of the following :

(1) Glass

(2) Metal

(3) Wood

(4) Either (1) or (3)

[AFMC-2000]

Q.12 The temperature on Celsius scale is \(25^{\circ} \mathrm{C}\). What is the corresponding temperature on the Fahrenheit scale :

(1) \(40^{\circ} \mathrm{C}\)

(2) \(77^{\circ} \mathrm{C}\)

(3) \(50^{\circ} \mathrm{C}\)

(4) \(45^{\circ}\)

[AFMC-2001] 

Q.13 Volume expansion coefficient of a gas at constant presure equal to :

[RPMT 2001]

(1) temperature

(2) proportional to square root of temperature

(3) inversely proportional to square root of temperature

(4) inversely proportional to temperature

Q.14 50 gm ice at \(0^{\circ} \mathrm{C}\) in insulator vessel, \(50 \mathrm{~g}\) water of \(100^{\circ} \mathrm{C}\) is mixed in it, then final temperature of the mixture is (neglect the heat loss) :

[RPMT 2001]

(1) \(10^{\circ} \mathrm{C}\)

(2) \(0^{\circ}<<\mathrm{T}_{\mathrm{m}}<20^{\circ} \mathrm{C}\)

(3) \(20^{\circ} \mathrm{C}\)

(4) Above \(20^{\circ} \mathrm{C}\)

Q.15 A bottle is filled with water at \(30^{\circ} \mathrm{C}\). When it is taken on the moon then :

[RPMT 2002]

(1) water will freeze

(2) water will boil

(3) water will decompose in hydrogen and oxygen

(4) nothing will happen to water

Q.16 Work done in converting one gram of ice at \(-10^{\circ} \mathrm{C}\) into steam at \(100^{\circ} \mathrm{C}\) is -

[PM PET/PMT 1998 EAMCET (MED.) 1995; MP PMT-2002]

(1) \(3045 \mathrm{~J}\)

(2) \(6056 \mathrm{~J}\)

(3) \(721 \mathrm{~J}\)

(4) \(616 \mathrm{~J}\)

Q.17 The ratio of radii of two spheres of same material is \(1: 4\), then the ratio of their heat capacities is

[RPMT 2003]

(1) \(\frac{1}{4}\)

(2) \(\frac{1}{16}\)

(3) \(\frac{1}{32}\)

(4) \(\frac{1}{64}\)

Q.18 If on heating liquid through \(80^{\circ} \mathrm{C}\), the mass expelled is \((1 / 100)\) th of mass still remaining, the coefficient of apparent expansion of liquid is :

[RPMT 2004]

(1) \(1.25 \times 10^{-4 /}{ }^{\circ} \mathrm{C}\)

(2) \(12.5 \times 10^{-4} /{ }^{\circ} \mathrm{C}\)

(3) \(1.25 \times 10^{-5} /{ }^{\circ} \mathrm{C}\)

(4) none of these

Q.19 \(10 \mathrm{~g}\) of ice at \(0^{\circ} \mathrm{C}\) is mixed with \(100 \mathrm{~g}\) of water at \(50^{\circ} \mathrm{C}\). What is the resultant temperature of mixture [AFMC-2005]

(1) \(31.2^{\circ} \mathrm{C}\)

(2) \(32.8^{\circ} \mathrm{C}\)

(3) \(36.7^{\circ} \mathrm{C}\)

(4) \(38.2^{\circ} \mathrm{C}\)

Q.20 An iron bar of length \(\ell\) and having a cross-section \(\mathrm{A}\) is heated from 0 to \(100^{\circ} \mathrm{C}\). It this bar is so held that it is not permitted to expand or bend, the force that is developed, is :

[RPMT 2005]

(1) inversely proportional to the cross-sectional area of the bar

(2) independent of the length of the bar

(3) inversely proportional to the length of the bar

(4) directly proportional to the length of the bar

Q.21 A steel scale measures the length of a copper wire as \(80.0 \mathrm{~cm}\), when both are at \(20^{\circ} \mathrm{C}\), the calibration temperature for the scale. What would the scale read for the length of the wire when both are at \(40^{\circ} \mathrm{C}\) ? Given : \(\alpha\) for steel \(=11 \times 10^{-10} /{ }^{\circ} \mathrm{C}\) and \(\alpha\) for \(\mathrm{Cu}=17 \times 10^{-6} /{ }^{\circ} \mathrm{C}\) :

(1) \(80.0096 \mathrm{~cm}\)

(2) \(80.0272 \mathrm{~cm}\)

(3) \(60.2 \mathrm{~cm}\)

(4) \(59.8 \mathrm{~cm}\)

[RPMT 2006] 

THERMAL EXPANSION, CALORIMETRY \& HEAT TRANSFER

Q.22 On a new scale of temperature (which is linear) and called the W scale, the freezing and boiling points of water are \(39^{\circ} \mathrm{W}\) and \(239^{\circ} \mathrm{W}\) respectively. What will be the temperature on the new scale, corresponding to a temperature of \(39^{\circ} \mathrm{C}\) on the Celsius scale ?

(1) \(78^{\circ} \mathrm{W}\)

(2) \(117^{\circ} \mathrm{W}\)

(3) \(200^{\circ} \mathrm{W}\)

(4) \(139^{\circ} \mathrm{C}\)

[AIPMT-2008]

Q.23 If the sphere of iron is heated, then its

(1) density increases

(2) volume increases

(3) radius decreases

(4) None of these

[RPMT 2009]

Q.24 The temperature of a body on kelvin scale is found to be \(\mathrm{x} \mathrm{K}\). When it is measured by Fahrenheit thermometer, it is found to be \(x^{\circ} \mathrm{F}\), then the value of \(x\) is :

(1) 30

(2) 313

(3) \(574.25\)

(4) \(301.25\)

[RPMT 2009]

Q.25 An electric kettle takes 4 A current at \(220 \mathrm{~V}\). How much time will it take to boil \(1 \mathrm{~kg}\) of water from temperature \(20^{\circ} \mathrm{C}\) ? The temperature of boiling water is \(100^{\circ} \mathrm{C}\). :

(1) \(6.3 \min\)

(2) \(8.4 \mathrm{~min}\)

(3) \(12.6 \mathrm{~min}\)

(4) \(4.2 \mathrm{~min}\)

[AIPMT-2009]

Q.26 \(540 \mathrm{~g}\) of ice at \(0^{\circ} \mathrm{C}\) is mixed with \(540 \mathrm{~g}\) of water at \(80^{\circ} \mathrm{C}\). What is the final temperature of the mixture.

(1) \(0^{\circ} \mathrm{C}\)

(2) \(40^{\circ} \mathrm{C}\)

(3) \(80^{\circ} \mathrm{C}\)

(4) \(0^{\circ} \mathrm{C}\)

[RPMT 2010]

Q.27 A constant pressure thermometer when immersed in ice cooled water gives volume reading \(47.5\) unit and when immersed in boiling liquid, it gives reading of 67 unit. What is the boiling point of the liquid.

[RPMT 2010]

(1) \(135^{\circ} \mathrm{C}\)

(2) \(125^{\circ} \mathrm{C}\)

(3) \(112^{\circ} \mathrm{C}\)

(4) \(100^{\circ} \mathrm{C}\)

Q.28 A beaker is completely filled with water at \(4^{\circ} \mathrm{C}\). The water will overflow if it is : [RPMT 2010]

(1) Warmed to temperature greater than \(4^{\circ} \mathrm{C}\)

(3) (1) and (2) both

(2) Cooled to temperature less than \(4^{\circ} \mathrm{C}\)

(4) None of the above

Q.29 300 calories of heat is supplied to raise the temperature of \(50 \mathrm{gm}\) of air from \(20^{\circ} \mathrm{C}\) to \(30^{\circ} \mathrm{C}\) without any change in its volume. Change in internal energy per gram of air is

(1) zero

(2) \(0.6\) calories

(3) \(1.2\) calories

(4) \(6.0\) calories

[RPMT 2011]

Q.30 The thermal capacity of any body is :

[RPMT 2011]

(1) a measure of its capacity of absorb heat

(2) a measure of its capacity to provide heat

(3) the quantity of heat required to raise its temperature by a unit degree

(4) the quantity of heat required to raise the temperature of a unit mass of the body by a unit degree

Q.31 Liquid oxygen at \(50 \mathrm{~K}\) is heated to \(300 \mathrm{~K}\) at constant pressure of \(1 \mathrm{~atm}\). The rate of heating is constant. Which one of the following graphs represents the variation of temperature with time?

[AIPMT-2012]

(2)   

(3)   

(4)  

Q.32 Steam at \(100^{\circ} \mathrm{C}\) is passed into \(20 \mathrm{~g}\) of water at \(10^{\circ} \mathrm{C}\) When water acquires a temperature of \(80^{\circ} \mathrm{C}\), the mass of water present will be:

[AIPMT 2014]

[Take specific heat of water \(=1 \mathrm{cal} \mathrm{g}^{-10} \mathrm{C}^{-1}\) and latent heat of steam \(=540 \mathrm{cal} \mathrm{g}^{-1}\) ]

(1) \(24 \mathrm{~g}\)

(2) \(31.5 \mathrm{~g}\)

(3) \(42.5 \mathrm{~g}\)

(4) \(22.5 \mathrm{~g}\)

Q.33 Figure shows the pressure - temperature phase diagram for water, the curves corresponding to sublimation, fusion and vaporisation respectively are

[RPMT_2014]

(1) \(\mathrm{AO}, \mathrm{OB}\) and \(\mathrm{OC}\)

(2) \(\mathrm{BO}, \mathrm{OC}\) and \(\mathrm{AO}\)

(3) \(\mathrm{OC}, \mathrm{BO}\) and \(\mathrm{AO}\)

(4) \(\mathrm{AO}, \mathrm{OC}\) and \(\mathrm{BO}\)

Q.34 A hot wire of copper is stretched at a temperature of \(150^{\circ} \mathrm{C}\) between two fixed walls. At what temperature will the wire break when it is cooled ? The breaking stress of copper is \(2.45 \times 10^{8} \mathrm{~N} / \mathrm{m}^{2}\) Young's modulus of copper \(=11.8 \times 10^{10} \mathrm{~N} / \mathrm{m}^{2}\), coefficient of linear expansion of copper \(=1.6 \times 10^{-5} /{ }^{\circ} \mathrm{C}\).

[RPMT_2014]

(1) \(20.2^{\circ} \mathrm{C}\)

(2) \(43.2^{\circ} \mathrm{C}\)

(3) \(64.9^{\circ} \mathrm{C}\)

(4) \(70.2^{\circ} \mathrm{C}\)

Q.35 a piece of ice falls from a height \(\mathrm{h}\) 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 \(\mathrm{h}\) is :[Latent heat of ice is \(3.4 \times 10^{5} \mathrm{~J} / \mathrm{Kg}\) and \(\mathrm{g}=10 \mathrm{~N} / \mathrm{kg}\) ]

(1) \(68 \mathrm{~km}\)

(2) \(34 \mathrm{~km}\)

(3) \(544 \mathrm{~km}\)

(4) \(136 \mathrm{~km}\)

[NEET 2016]

Q.36 Two identical bodies are made of a material for which the heat capacity increases with temperature. One of these is at \(100^{\circ} \mathrm{C}\), while the other one is at \(0^{\circ} \mathrm{C}\). If the two bodies are brought into contact, then assuming no heat loss, the final common temperature is

(1) \(0^{\circ} \mathrm{C}\)

(2) \(50^{\circ} \mathrm{C}\)

(3) more then \(50^{\circ} \mathrm{C}\)

(4) less than \(50^{\circ} \mathrm{C}\) but greater than \(0^{\circ} \mathrm{C}\)

[NEET 2016]

Q.37 The temperature inside a refrigerator is \(\mathrm{t}_{2}{ }^{\circ} \mathrm{C}\) and the room temperature is \(\mathrm{t}_{1}{ }^{\circ} \mathrm{C}\). The amount of heat delivered to the room for each joule of electrical energy consumed ideally will be

[NEET 2016]

(1) \(\frac{t_{1}+t_{2}}{t_{1}+273}\)

(2) \(\frac{t_{1}}{t_{1}-t_{2}}\)

(3) \(\frac{t_{1}+273}{t_{1}-t_{2}}\)

(4) \(\frac{t_{2}+273}{t_{1}-t_{2}}\) 

THERMAL EXPANSION, CALORIMETRY \& HEAT TRANSFER

Q.38 Coefficient of linear expansion of brass and steel rods are \(\alpha_{1}\) and \(\alpha_{2}\). Lengths of brass and steel rods are \(\ell_{1}\) and \(\ell_{2}\) respectively. If \(\left(\ell_{2}-\ell_{1}\right)\) is maintained same at all temperatures, which one of the following relations holds good?

(1) \(\alpha_{1} \ell_{1}=\alpha_{2} \ell_{2}\)

(2) \(\alpha_{1} \ell_{2}=\alpha_{2} \ell_{1}\)

(3) \(\alpha_{1} \ell_{2}^{2}=\alpha_{2} \ell_{1}^{2}\)

\((4) \alpha_{1}^{2} \ell_{2}=\alpha_{2}^{2} \ell_{1}\)

[NEET 2016]

HEAT TRANSFER

Q.39 A body radiates energy \(5 \mathrm{~W}\) at a temperature of \(127^{\circ} \mathrm{C}\). If the temperature is increased to \(927^{\circ} \mathrm{C}\), then it radiates energy at the rate of :

[AFMC 2000]

(1) \(410 \mathrm{~W}\)

(2) \(81 \mathrm{~W}\)

(3) \(405 \mathrm{~W}\)

(4) \(200 \mathrm{~W}\)

Q.40 In which case the thermal connectivity increases from left to right :

(1) Al, Cu, Ag

(2) \(\mathrm{Ag}, \mathrm{Cu}, \mathrm{Al}\)

(3) \(\mathrm{Cu}, \mathrm{Ag}, \mathrm{Al}\)

(4) \(\mathrm{Al}, \mathrm{Ag}, \mathrm{Cu}\)

[AFMC-2000]

Q.41 Which of the following is nearest to blackbody-

(1) An enclosure with a small hole

(2) Carbon black

(3) Abonite

(4) None of these

[CPET-2002]

Q.42 Area of cross-section of two rods of equal lengths are \(\mathrm{A}_{1}\) and \(\mathrm{A}_{2}\) and thermal conductivities are \(\mathrm{K}_{1}\) and \(\mathrm{K}_{2}\). Specific heats are \(\mathrm{S}_{1}\) and \(\mathrm{S}_{2}\). condition for equal heat flow is-

[CPMT- 2002]

(1) \(\mathrm{K}_{1}=\mathrm{K}_{2}\)

(2) \(\mathrm{K}_{1} \mathrm{~S}_{1}=\mathrm{K}_{2} \mathrm{~S}_{2}\)

(3) \(\frac{\mathrm{K}_{1}}{\mathrm{~A}_{1} \mathrm{~S}_{1}}=\frac{\mathrm{K}_{2}}{\mathrm{~A}_{2} \mathrm{~S}_{2}}\)

(4) \(\mathrm{K}_{1} \mathrm{~A}_{1}=\mathrm{K}_{2} \mathrm{~A}_{2}\)

Q.43 If two metallic plates of equal thickness and thermal conductivities \(\mathrm{K}_{1}\) and \(\mathrm{K}_{2}\) are put together face to face and a common plate is constructed, then the equivalent thermal conductivity of this plate will be-

[CPMT-2002]

(1) \(\frac{\mathrm{K}_{1} \mathrm{~K}_{2}}{\mathrm{~K}_{1}+\mathrm{K}_{2}}\)

(2) \(\frac{2 \mathrm{~K}_{1} \mathrm{~K}_{2}}{\mathrm{~K}_{1}+\mathrm{K}_{2}}\)

(3) \(\frac{\left(\mathrm{K}_{1}^{2}+\mathrm{K}_{2}^{2}\right)^{3 / 2}}{\mathrm{~K}_{1} \mathrm{~K}_{2}}\)

(4) \(\frac{\left(\mathrm{K}_{1}^{2}+\mathrm{K}_{2}^{2}\right)^{3 / 2}}{2 \mathrm{~K}_{1} \mathrm{~K}_{2}}\)

Q.44 The presence of gravitational field is required for the heat transfer by :

[AIPMT-2000]

(1) conduction

(2) stirring of liquids

(3) natural convection

(4) radiation

Q.45 A black body has maximum wavelength \(\lambda_{\mathrm{m}}\) at temperature \(2000 \mathrm{~K}\). Its corresponding wavelength at temperature \(3000 \mathrm{~K}\) will be :

[AIPMT-2001]

(1) \(\frac{3}{2} \lambda_{m}\)

(2) \(\frac{2}{3} \lambda_{m}\)

(3) \(\frac{4}{9} \lambda_{m}\)

(4) \(\frac{9}{4} \lambda_{m}\)

Q.46 A cylindrical rod having temperature \(\mathrm{T}_{1}\) and \(\mathrm{T}_{2}\) at its end. The rate of flow of heat is \(\mathrm{Q}_{1}\) cal \(/ \mathrm{sec}\). If all the linear dimensions are doubled keeping temperature constant, then the rate of flow of heat \(\mathrm{Q}_{2}\) will be :

(1) \(4 Q_{1}\)

(2) \(2 Q_{1}\)

(3) \(Q_{1} / 4\)

(4) \(Q_{1} / 2\)

[AIPMT-2001]

Q.47 If temperature of body increases by \(10 \%\), then increase in radiated energy of the body is :

[RPMT 2001, 2002]

(1) \(10 \%\)

(2) \(40 \%\)

(3) \(46 \%\)

(4) \(1000 \%\) 

Q.48 Which of the following is true statement?

[RPMT 2001]

(1) A good absorber is bad conductor

(2) Each body emits and absorb radiation at each temperature

(3) In a black body energy of emitted radiation is equal for all wavelength

(4) Planck's law gives the relation between maximum wavelength of black body radiation and its tem- perature.

Q.49 Wien's law is concerned with :

(1) Relation between emissivity and absorptivity of a radiating surface

(2) Total radiation, emitted by a hot surface

(3) An expression for spectral distribution of energy of a radiation from any source

(4) A relation between the temperature of a black body and the wavelength at which there is maximum radiant energy per unit wavelength

Q.50 Radiation from which of the following sources, approximates black body radiation best?

(1) A tungsten lamp

(2) Sodium flame

(3) Sodium lamp

(4) A hole in a cavity, maintained at constant temperature

[AIPMT-2002]

Q.51 Two rods of thermal conductivities \(\mathrm{K}_{1}\) and \(\mathrm{K}_{2}\), cross-sections \(\mathrm{A}_{1}\) and \(\mathrm{A}_{2}\) and specific heats \(\mathrm{S}_{1}\) and \(\mathrm{S}_{2}\) are of equal lengths. The temperatures of two ends of each rod are \(\mathrm{T}_{1}\) and \(\mathrm{T}_{2}\). The rate of flow of heat at the steady state will be equal if:

[AIPMT-2002]

(1) \(\frac{K_{1}}{\mathrm{~A}_{1} \mathrm{~S}_{1}}=\frac{\mathrm{K}_{2}}{\mathrm{~A}_{2} \mathrm{~S}_{2}}\)

(2) \(\mathrm{K}_{\mathrm{a}} \mathrm{A}_{1}=\mathrm{K}_{2} \mathrm{~A}_{2}\)

(3) \(\mathrm{K}_{1} \mathrm{~S}_{1}=\mathrm{K}_{2} \mathrm{~S}_{2}\)

(4) \(\mathrm{A}_{1} \mathrm{~S}_{1}=\mathrm{A}_{2} \mathrm{~S}_{2}\)

Q.52 A square is made of four rods of same material one of the diagonal of a square is at temperature difference \(100^{\circ} \mathrm{C}\), then the temperature difference of second diagonal :

[RPMT 2002]

(1) \(0^{\circ} \mathrm{C}\)

(2) \(\frac{100}{\ell}\)

(3) \(\frac{100}{2 \ell}\)

(4) \(100^{\circ} \mathrm{C}\)

Q.53 For a perfectly black body, its absorptive power is :

(1) 1

(2) \(0.5\)

(3) 0

(4) Infinity

[AFMC-2003]

Q.54 Three objects coloured black, gray and white can withstand hostile conditions up to \(2800^{\circ} \mathrm{C}\). These objects are thrown into a furnace here each of them attains a temperature of \(2000^{\circ} \mathrm{C}\). Which object will glow brightest :

(1) The white object

(3) All glow with equal brightness

(2) The black object

(4) Gray object

[AFMC-2003]

Q.55 Consider a compound slab consisting of two different material having equal thicknesses and thermal conductivities \(\mathrm{K}\) and \(2 \mathrm{~K}\). Respectively. The equivalent thermal conductivity of the slab is :

[AIPMT-2003]

(1) \(\frac{4}{3} \mathrm{~K}\)

(2) \(\frac{2}{3} \mathrm{~K}\)

(3) \(\sqrt{3} \mathrm{~K}\)

(4) \(3 \mathrm{~K}\)

Q.56 If \(\lambda_{\mathrm{m}}\) denotes the wavelength at which the radiative emission from a black body at a temperature \(\mathrm{T} \mathrm{K}\) is maximum, then-

(1) \(\lambda_{m} \propto T^{4}\)

(3) \(\lambda_{m} \propto T\)

(2) \(\lambda_{\mathrm{m}}\) is independent of T

(4) \(\lambda_{\mathrm{m}} \propto T^{-1}\)

[CPMT - 2004] 

THERMAL EXPANSION, CALORIMETRY \& HEAT TRANSFER

Q.57 Which of the following circular rods (given radius \(r\) and length \(\ell\) ), each made of the same material and whose ends are maintained at the same temperature will conduct most heat?

[AIPMT-2005]

(1) \(\mathrm{r}=\mathrm{r}_{0} ; \ell=\ell_{0}\)

(2) \(\mathrm{r}=2 \mathrm{r}_{0} ; \ell=\ell_{0}\)

(3) \(\mathrm{r}=\mathrm{r}_{0} ; \ell=2 \ell_{0}\)

(4) \(\mathrm{r}=2 \mathrm{r}_{0} ; \ell=2 \ell_{0}\)

Q.58 Which of the following processes is reversible?

(1) Transfer of heat by radiation

(2) Electrical heating of nichrome wire

(3) Transfer of heat by conduction

(4) Isothermal compression

[CPMT 2005]

Q.59 The colour of a star indicates its :

(1) temperature

(2) distance

(3) velocity

(4) size

[RPMT 2005]

Q.60 A black body is at \(1227^{\circ} \mathrm{C}\) emits radiations with maximum intensity at a wavelength of 5000  . If the temperature of the body is increased by \(1000^{\circ} \mathrm{C}\), the maximum intensity will be observed at :

(1) 5000

(2)6000

(3) 3000

(4) 4000

[AIPMT-2006]

Q.61 A black body is at \(727^{\circ} \mathrm{C}\). It emits energy at a rate which is proportional to :

\((1)(1000)^{4}\)

\((2)(1000)^{2}\)

\((3)(727)^{4}\)

(4) \((727)^{2}\)

[AIPMT-2007]

Q.62 Assuming the sun to have a spherical outer surface of radius \(r\), radiating like a black body at temperature \(\mathrm{t}^{\circ} \mathrm{C}\), the power received by a unit surface, (normal to the incident rays) at a distance \(\mathrm{R}\) from the center of the sun is

[CPMT 2007]

(1) \(\frac{4 \pi r^{2} t^{4}}{R^{2}}\)

(2) \(\frac{r^{2} \sigma(t+273)^{4}}{4 \pi R^{2}}\)

(3) \(\frac{16 \pi^{2} r^{2} \sigma t^{4}}{R^{2}}\)

(4) \(\frac{r^{2} \sigma(t+273)^{2}}{R^{2}}\)

Q.63 A black body is at \(727^{\circ} \mathrm{C}\). It emits energy at a rate which is proprotional to

[CPMT 2007]

(1) \((277)^{2}\)

\((2)(1000)^{4}\)

(3) \((1000)^{2}\)

(4) \((727)^{4}\)

Q.64 A black body at \(227^{\circ} \mathrm{C}\) radiates heat at the rate of \(7 \mathrm{cals} / \mathrm{cm}^{2} \mathrm{~s}\). At a temperature of \(727^{\circ} \mathrm{C}\), the rate of heat radiated in the same units will be :

(1) 50

(2) 112

(3) 80

(4) 60

[AIPMT 2009]

Q.65 The two ends of a rod of length \(L\) and a uniform cross-sectional area \(A\) kept at two temperatures \(T_{1}\) and \(\mathrm{T}_{2}\left(\mathrm{~T}_{1}>\mathrm{T}_{2}\right)\). The rate of heat transfer, \(\frac{\mathrm{dQ}}{\mathrm{dt}}\), through the rod in a steady state is given by [CPMT 2009]

(1) \(\frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{\mathrm{KL}\left(\mathrm{T}_{1}-\mathrm{T}_{2}\right)}{\mathrm{A}}\)

(2) \(\frac{\mathrm{dQ}}{\mathrm{dt}}=\frac{K\left(T_{1}-T_{2}\right)}{L A}\)

(3) \(\frac{d Q}{d t}=K L A\left(T_{1}-T_{2}\right)\)

(4) \(\frac{d Q}{d t}=\frac{K A\left(T_{1}-T_{2}\right)}{L}\)

Q.66 A cylindrical metallic rod in thermal contact with two reservoirs of heat at its two ends conducts an amount of heat \(\mathrm{Q}\) in time \(t\). The metallic rod is melted and the material is formed into a rod of half the radius of the origin rod. What is the amount of heat conducted by the new rod, when placed in thermal contact with the two reservoirs in time?

[AIPMT-2010]

(1) \(\frac{Q}{4}\)

(2) \(\frac{Q}{16}\)

(3) \(2 \mathrm{Q}\)

(4) \(\frac{Q}{2}\) 

THERMAL EXPANSION, CALORIMETRY \& HEAT TRANSFER

Q.67 The total radiant energy per unit area, normal to the direction of incidence, received at a distance \(\mathrm{R}\) from the centre of a star of radius \(\mathrm{r}\), whose outer surface radiates as a black body at a temperature \(\mathrm{T}\) \(\mathrm{K}\) is given by :

[AIPMT-2010]

(1) \(\frac{\sigma r^{2} \mathrm{~T}^{4}}{\mathrm{R}^{2}}\)

(2) \(\frac{\sigma r^{2} T^{4}}{4 \pi r^{2}}\)

(3) \(\frac{\sigma r^{4} T^{4}}{r^{4}}\)

(4) \(\frac{4 \pi \sigma r^{2} T^{4}}{R^{4}}\)

Q.68 If the radius of a star is \(\mathrm{R}\) and it acts as a black body, what would be the temperature of the star, in which the rate of energy production is \(\mathrm{Q}\) ?

[AIPMT-2012]

(1) \(Q / 4 \pi R^{2} \sigma\)

(2) \(\left(\mathrm{Q} / 4 \pi R^{2} \sigma\right)^{-1 / 2}\)

(3) \(\left(4 p R^{2} Q / \sigma\right)^{1 / 4}\)

(4) \(\left(\mathrm{Q} / 4 \pi \mathrm{R}^{2} \sigma\right)^{1 / 4}\)

Q.69 Certain quantity of water cools from \(70^{\circ} \mathrm{C}\) to \(60^{\circ} \mathrm{C}\) in the first 5 minutes and to \(54^{\circ} \mathrm{C}\) in the next 5 minutes. The temperature of the surroundings is

[AIPMT-2014]

(1) \(42^{\circ} \mathrm{C}\)

(2) \(10^{\circ} \mathrm{C}\)

(3) \(45^{\circ} \mathrm{C}\)

(4) \(20^{\circ} \mathrm{C}\)

Q.70 On observing light from three different stars \(\mathrm{P}, \mathrm{Q}\) and \(\mathrm{R}\), it was found that intensity of violet colour is maximum in the spectrum of \(\mathrm{P}\), the intensity of green colour is maximum in the spectrum of \(\mathrm{R}\) and the intensity of red colour is maximum in the spectrum of \(\mathrm{Q}\). If \(\mathrm{T}_{\mathrm{P}}, \mathrm{T}_{\mathrm{Q}}\) and \(\mathrm{T}_{\mathrm{R}}\) are the respective absolute temperatures of \(\mathrm{P}, \mathrm{Q}\) and \(\mathrm{R}\), then it can be concluded from the above observations that

[AIPMT NEET 2015]

(1) \(T_{P}>T_{R}>T_{Q}\)

(2) \(\mathrm{T}_{\mathrm{P}}<\mathrm{T}_{\mathrm{R}}<\mathrm{T}_{\mathrm{Q}}\)

(3) \(\mathrm{T}_{\mathrm{P}}<\mathrm{T}_{\mathrm{Q}}<\mathrm{T}_{\mathrm{R}}\)

(4) \(\mathrm{T}_{\mathrm{P}}>\mathrm{T}_{\mathrm{Q}}>\mathrm{T}_{\mathrm{R}}\)

Q.71 The two ends of a metal rod are maintained at temperatures \(100^{\circ} \mathrm{C}\) and \(110^{\circ} \mathrm{C}\). The rate of heat flow in the rod is found to be \(4.0 \mathrm{~J} / \mathrm{s}\). If the ends are maintained at temperatures \(200^{\circ} \mathrm{C}\) and \(210^{\circ} \mathrm{C}\), the rate of heat flow will be :[AIPMT NEET 2015]

(1) \(16.8 \mathrm{~J} / \mathrm{s}\)

(2) \(8.0 \mathrm{~J} / \mathrm{s}\)

(3) \(4.0 \mathrm{~J} / \mathrm{s}\)

(4) \(44.0 \mathrm{~J} / \mathrm{s}\)

Q.72 A block body is at a temperature of \(5760 \mathrm{~K}\). The energy of radiation emitted by the body at wavelength \(250 \mathrm{~nm}\) is \(\mathrm{U}_{1}\) at wavelength \(500 \mathrm{~nm}\) is \(\mathrm{U}_{2}\) and that at \(1000 \mathrm{~nm}\) is \(\mathrm{U}_{3}\). Wien's constant, \(\mathrm{b}=2.88 \times 10^{6}\) \(\mathrm{nmK}\). Which of the following is correct?

[NEET 2016]

(1) \(\mathrm{U}_{2}>\mathrm{U}_{1}\)

(2) \(\mathrm{U}_{1}=0\)

(3) \(\mathrm{U}_{3}=0\)

(4) \(\mathrm{U}_{1}>\mathrm{U}_{2}\)

Q.73 A body cools from a temperature \(3 \mathrm{~T}\) to \(2 \mathrm{~T}\) in 10 minutes. The room temperature is \(\mathrm{T}\). Assume that Newton's law of cooling is applicable. The temperature of the body at the end of next 10 minutes will be

[NEET 2016]

(1) \(\mathrm{T}\)

(2) \(\frac{7}{4} \mathrm{~T}\)

(3) \(\frac{3}{2} \mathrm{~T}\)

(4) \(\frac{4}{3} \mathrm{~T}\) 

THERMAL EXPANSION, CALORIMETRY \& HEAT TRANSFER

Q.74 Two rods Aand B ofdifferent materials are welded together as shown in figure. Their thermal conductivities are \(\mathrm{K}_{1}\) and \(\mathrm{K}_{2}\). The thermal conductivity of the composite rod will be

[NEET2017]

(1) \(\frac{K_{1}+K_{2}}{2}\)

(2) \(\frac{3\left(K_{1}+K_{2}\right)}{2}\)

(3) \(\mathrm{K}_{1}+\mathrm{K}_{2}\)

(4) \(2\left(\mathrm{~K}_{1}+\mathrm{K}_{2}\right)\)

Q.75 A spherical black body with a radius of \(12 \mathrm{~cm}\) radiates 450 watt power at \(500 \mathrm{~K}\). If the radius were halved and the temperature doubled, the power radiated in watt would be :

[NEET2017]

(1) 225

(2) 450

(3) 1000

(4) 1800 

EXERCISE-4 (B)

PREVIOUS YEAR'S QUESTIONS (AIIMS)

THERMAL EXPANSION \& CALORIMETRY

Q.1 A centigrade and a Fahrenheit thermometer are dipped in boiling water. The water temperature is lowered until the Fahrenheit thermometer registers \(140^{\circ}\). What is the fall in temperature as registered by the Centigrade thermometer :

(1) \(30^{\circ}\)

(2) \(40^{\circ}\)

(3) \(60^{\circ}\)

(4) \(81^{\circ}\)

[AIIMS-1998]

Q.2 Assertion : Woollen clothes keep the body warm in winter.

Reason : Air is a bad conductor of heat.

[AIIMS-2002]

(1) Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

(2) Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.

(3) Assertion is true but the Reason is false

(4) Assertion and Reason both are false

Q.3 A metallic ball and highly stretched spring are made of the same material and have the same mass. They are heated so that they melt, the latent heat required :

(1) Are the same for both

(2) Is greater for the ball

(3) Is greater for the spring

(4) For the two may or may not be the same depending upon the metal

[AIIMS-2002]

Q.4 Assertion : Temperatures near the sea coast are moderate.

Reason : Water has a high thermal conductivity.

[AIIMS-2003]

(1) Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

(2) Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.

(3) Assertion is true but the Reason is false

(4) Assertion and Reason both are false

Q.5 Assertion : The melting point of ice decreases with increase of pressure.

Reason : Ice contracts on melting.

[AIIMS-2004]

(1) Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

(2) Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.

(3) Assertion is true but the Reason is false

(4) Assertion and Reason both are false

Q.6 Two rigid boxes containing different ideal gases are placed on a table. Box A contains one mole of nitrogen at temperature \(T_{0}\), While Box B contains one mole of helium at temperature \((7 / 3) T_{0}\). The boxes are then put into thermal contact with each other and heat flows between them until the gases reach a common final temperature (lgnore the heat capacity of boxes). Then, the final temperature of the gases, \(\mathrm{T}_{\mathrm{f}}\), in term of \(\mathrm{T}_{0}\) is

[AIIMS 2008]

(1) \(\mathrm{T}_{\mathrm{f}}=\frac{7}{3} \mathrm{~T}_{0}\)

(2) \(T_{f}=\frac{3}{2} T_{0}\)

(3) \(T_{f}=\frac{5}{2} T_{0}\)

(4) \(T_{f}=\frac{3}{7} T_{0}\) 

THERMAL EXPANSION, CALORIMETRY \& HEAT TRANSFER

Q.7 A clock with a metal pendulum beating seconds keeps correct time at \(0^{\circ} \mathrm{C}\). If it loses \(12.5 \mathrm{~s}\) a day at \(25^{\circ} \mathrm{C}\), the coefficient of linear expansion of metal pendulum is :

[AIIMS-2010]

(1) \(\frac{1}{86400} /{ }^{\circ} \mathrm{C}\)

(2) \(\frac{1}{43200} /{ }^{\circ} \mathrm{C}\)

(3) \(\frac{1}{14400} /{ }^{\circ} \mathrm{C}\)

(4) \(\frac{1}{28800} /{ }^{\circ} \mathrm{C}\)

HEAT TRANSFER

Q.8 The intensity of radiation emitted by the sun has its maximum value at a wavelength of \(510 \mathrm{~nm}\) and that emitted by the north star has the maximum value at \(350 \mathrm{~nm}\). If these stars behave like black bodies, then the ratio of the surface temperature of the sun and north star is :

(1) \(1.46\)

(2) \(0.69\)

(3) \(1.21\)

(4) \(0.83\)

[AIIMS 2000]

Q.9 The amount of radiation emitted by a perfectly black body is proportional to : [AIIMS-2000]

(1) Temperature on ideal gas scale

(2) Fourth root of temperature on ideal gas scale

(3) Fourth power of temperature on ideal gas scale

(4) Source of temperature on ideal gas scale

Q.10 The temperatures of two bodies A and B are respectively \(727^{\circ} \mathrm{C}\) and \(327^{\circ} \mathrm{C}\). The ratio \(\mathrm{H}_{\mathrm{A}}: \mathrm{H}_{\mathrm{B}}\) of the rates of heat radiated by them is :

[AIIMS 2000]

(1) \(727: 327\)

(2) \(5: 3\)

(3) \(25: 9\)

(4) \(625: 81\)

Q.11 Assertion : Rate of radiation of heat is proportional to the fourth power of absolute temperature. Reason : Bodies radiate heat at all temperatures.

[AIIMS-2002]

(1) Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

(2) Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.

(3) Assertion is true but the Reason is false

(4) Assertion and Reason both are false

Q.12 Assertion : Blue star is at high temperature than red star.

Reason : Wien's displacement law states that \(\mathrm{T} \propto\left(1 / \lambda_{\mathrm{m}}\right)\)

[AIIMS-2002]

(1) Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

(2) Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.

(3) Assertion is true but the Reason is false

(4) Assertion and Reason both are false

Q.13 A black body radiates \(20 \mathrm{~W}\) at temperature \(227^{\circ} \mathrm{C}\). If temperature of the black body is changed to \(727^{\circ} \mathrm{C}\) then its radiating power will be :

[AIIMS-2003]

(1) \(120 \mathrm{~W}\)

(2) \(240 \mathrm{~W}\)

(3) \(320 \mathrm{~W}\)

(4) \(360 \mathrm{~W}\)

Q.14 Assertion : It is hotter over the top of a fire than at the same distance on the sides. Reason : Air surrounding the fire conducts more heat upwards.

[AIIMS-2003]

(1) Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

(2) Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.

(3) Assertion is true but the Reason is false

(4) Assertion and Reason both are false 

THERMAL EXPANSION, CALORIMETRY \& HEAT TRANSFER

Q.15 Suppose the sun expands so that its radius becomes 100 times its present radius and its surface temperature becomes half of its present value. The total energy emitted by it then will increase by a factor of:

(1) \(10^{4}\)

(2) 625

(3) 256

(4) 16

[AIIMS-2004]

Q.16 Assertion : A body that is a good radiator is also a good absorber of radiation at a given wavelength. Reason : According to Kirchhoff's law the absorptiviity of a body is equal to its emissivity at a given wavelength.

[AIIMS-2005]

(1) Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

(2) Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.

(3) Assertion is true but the Reason is false

(4) Assertion and Reason both are false

Q.17 Assertion : For higher temperature, the peak emission wavelength of a black body shifts to lower wavelength.

Reason : Peak emission wavelength of a blackbody is proportional to the fourth power of temperature.

[AIIMS-2005]

(1) Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

(2) Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.

(3) Assertion is true but the Reason is false

(4) Assertion and Reason both are false

Q.18 Flash light equipped with a new set of batteries, produces bright white light. As the batteries wear out

[AIIMS - 2006]

(1) The light intensity gets reduced with no change in its colour

(2) Light colour changes first to yellow and then red with no change in intensity

(3) It stops working suddenly while giving white light

(4) Colour changes to red and also intensity gets reduced

Q.19 Assertion : Perspiration from human body helps in cooling the body.

Reason: A thin layer of water on the skin enhances its emissivity.

[AIIMS-2006]

(1) Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

(2) Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.

(3) Assertion is true but the Reason is false

(4) Assertion and Reason both are false

Q.20 We have seen that a gamma-ray does of \(\mathrm{Gy}\) is lethal to half the people exposed to it. If the equivalent energy were absorbed as heat, what rise in body temperature would result :

(1) \(300 \mu \mathrm{K}\)

(2) \(700 \mu \mathrm{K}\)

(3) \(455 \mu \mathrm{K}\)

(4) \(390 \mu \mathrm{K}\)

[AIIMS-2007]

Q.21 Assertion : While measuring the thermal conductivity of liquid experimentally, the upper layer is kept hot and the lower layer is kept cold.

Reason : This avoids heating of liquid by convection.

[AIIMS-2007]

(1) Assertion and Reason are true and the Reason is the correct explanation of the Assertion.

(2) Assertion and Reason are true but the Reason is not a correct explanation of the Assertion.

(3) Assertion is true but the Reason is false

(4) Assertion and Reason both are false 

THERMAL EXPANSION, CALORIMETRY \& HEAT TRANSFER

Q.22 Two rigid boxes containing different ideal gases are placed on a table. Box A contains one mole of nitrogen at temperature \(\mathrm{T}_{0}\), while box \(\mathrm{B}\) contains one mole of helium at temperature \((7 / 3) \mathrm{T}_{0}\). The boxes are then put into thermal contact with each other and heat flows between them until the gases reach a common final temperature (Ignore the heat capacity of boxes). Then, the final temperature of the gases, \(\mathrm{T}_{\mathrm{f}}\), in terms of \(\mathrm{T}_{0}\) is :

[AIIMS-2008]

(1) \(\mathrm{T}_{\mathrm{f}}=\frac{7}{3} \mathrm{~T}_{0}\)

(2) \(\mathrm{T}_{\mathrm{f}}=\frac{3}{2} \mathrm{~T}_{0}\)

(3) \(\mathrm{T}_{\mathrm{f}}=\frac{5}{2} \mathrm{~T}_{0}\)

(4) \(\mathrm{T}_{\mathrm{f}}=\frac{3}{7} \mathrm{~T}_{0}\)

Q.23 A metal plate \(4 \mathrm{~mm}\) thick has a temperature difference of \(32^{\circ} \mathrm{C}\) between its faces. It transmits \(200 \mathrm{kcal} / \mathrm{h}\) through an area of \(5 \mathrm{~cm}^{2}\). Thermal conductivity of the material is :

[AIIMS-2010]

(1) \(58.33 \mathrm{~W} / \mathrm{m}-{ }^{\circ} \mathrm{C}\)

(2) \(33.58 \mathrm{~W} / \mathrm{m}-{ }^{\circ} \mathrm{C}\)

(3) \(5 \times 10^{-4} \mathrm{~W} / \mathrm{m}{ }^{\circ} \mathrm{C}\)

(4) None of these

Q.24 The temperature of a body is increased from \(-73^{\circ} \mathrm{C}\) to \(327^{\circ} \mathrm{C}\). Then the ratio of emissive power is

(1) \(1 / 9\)

(2) \(1 / 27\)

(3) 27

(4) 81

[AIIMS-2016] 

(Potential Problems Based on CBSE)

THERMAL EXPANSION \& CALORIMETRY

Mark Questions

Q.1 What is the principle of calorimetry.

Q.2 At what temperature do the Celsius and Fahrenheit scales coincide?

Q.3 Define temperature.

Q.4 Define specific heat of a body.

Q.5 Plot a graph showing the variation of specific heat of water with temperature.

Q.6 What is the value of specific heat of water in S.I. units ? Does it vary with temperature?

Q.7 Why are we advised to store medicine below \(86^{\circ}\) ?

Q.8 What is the dimensional formulae of coefficient of linear expansion \((\alpha)\).

Q.9 What do you mean by thermal stress?

Marks Questions

Q.10 What is calorimetry? What is the principle of calorimetre?

Q.11 Define water equivalent

Q.12 If an area measured on the surface of a solid body is \(\mathrm{A}_{0}\) at some initial temperature and then changes by \(\Delta \mathrm{A}\) when the temperature changes by \(\Delta \mathrm{T}\), show that \(\Delta \mathrm{A}=2 \alpha \mathrm{A}_{0} \Delta \mathrm{T}\), where \(\alpha\) is the coefficient of linear expansion.

Q.13 You feel sick and are told that you have a temperature of \(40.2^{\circ} \mathrm{C}\). What is your temperature in \({ }^{\circ} \mathrm{F}\) ? Should you be concemed?

Q.14 The scale on a steel metre stick is calibrated at \(15^{\circ} \mathrm{C}\). What is the error in the reading of a length of \(60 \mathrm{~cm}\) at \(27^{\circ} \mathrm{C} ? \alpha_{\text {steel }}=1.2 \times 10^{-5}{ }^{0} \mathrm{C}^{-1}\).

Q.15 What do you mean by latent heat? Explain.

Q.16 Obtain the expression for the force developed in a rod which is under the thermal stress.

Q.17 Differentiate between evaporation and boiling.

Q.18 How the fishes can survive in the extreme winter, when ponds and lakes are frozen? Q.19 What does a glass dish shatter when taken from the oven andput into cold water.

Marks Questions

Q.20 Explain, what is meant by the coefficients of linear \((\alpha)\), \(\operatorname{superficial}(\beta)\) and cubical expansion \((\gamma)\) of a solid. Give their units. Find the relationship between them.

HEAT TRANSFER

Mark Questions

Q.21 What is the S.I. unit of thermal conductivity?

Q.22 What is the shift in the colour of light when the temperature increase?

Q.23 Why does a blackbody appear brighter than the pollished surface when both are heated to the same temperature?

Q.24 A beak full of hot water is placed on wooden table.does it lose heat? If yes, in what way?

Q.25 It is warmer to ear two thin shirts than a single thick shirt of the same material. Why?

Marks Questions

Q.26 Even when earth receives solar energy, why is it not getting warmed up continuously?

Q.27 Define solar constant.

Q.28 Distinguish the radiation and convection methods of heat transfer.

Q.29 Show that the SI units of thermal conductivity is \(\mathrm{W} / \mathrm{m} \mathrm{K}\).

Q.30 Two rods of same length and material transfer a given amount of heat in \(12 \mathrm{~s}\), when they are joined end to end. But when they are joined lengthwise, find time taken to transfer the same amount of heat in same condition.

Marks Questions

Q.31 List the salient features of heat radiations.

Q.32 What are the basic requirements of a cooking utensil in respect of specific heat, thermal conductivity and coefficient of expansion?

Q.33 State Kirchhoff's law of black body radiations.

Q.34 Two rods of the same area of cross-section, but of length \(\ell_{1}\) and \(\ell_{2}\) and conductivities \(\mathrm{K}_{1}\) and \(\mathrm{K}_{2}\) are joined in series. Show that the combination is equivalent of a material of conductivity \(\mathrm{K}=\frac{\ell_{1}+\ell_{2}}{\left(\frac{\ell_{1}}{\mathrm{~K}_{1}}\right)+\left(\frac{\ell_{2}}{\mathrm{~K}_{2}}\right)}\)

Q.35 Derive the expression for the rate of flow of heat energy through a conductor maintained at different temperature at its two ends.

Q.36 Define the coefficient of thermal conductivity and expalin the formula used. Why do metalshave higher conductivity than insulator? 

THERMAL EXPANSION, CALORIMETRY \& HEAT TRANSFER

Q.37 Why do electrons in insulator not contribute to its conductivity.

Q.38 Find the thermal resistance of an aluminium rod of length \(10 \mathrm{~cm}\) and area of cross-section \(2 \mathrm{~cm}^{2}\). The heat current is along the length of rod. Thermal conductivity of aluminium \(=200 \mathrm{Wm}^{-1} \mathrm{~K}^{-1}\).

Q.39 A hot body placed in air is cooled according to Newton's law of cooling, the rate of decrease of temperature being \(\mathrm{K}\) times the temperature difference from the surroundings. Starting from \(t=0\), find the time in which the body will lose half the maximum temperature it can lose.