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question_answer1) Is temperature a macroscopic or microscopic concept?
question_answer2) What is dynamical theory of heat?
question_answer3) Two thermometers are constructed in the same way except that one has a spherical bulb and the other an elongated cylindrical bulb. Which of the two will respond quickly to temperature changes?
question_answer4) Why a clinical thermometer should not be sterilized by boiling?
question_answer5) Why should a thermometer bulb have a small heat capacity?
question_answer6) What do you mean by triple point of water? Why it is unique?
question_answer7) Why are gas thermometers are more sensitive than mercury thermometers?
question_answer8) Can the temperature of a body be negative on the kelvin scale?
question_answer9) Mercury boils at \[\mathbf{357}{}^\circ \text{ }\mathbf{C}\] How can then a mercury thermometer be used to measure temperature up to\[\mathbf{500}{}^\circ \mathbf{C}\]?
question_answer10) Why the temperatures above \[\mathbf{1200}{}^\circ \text{ }\mathbf{C}\] cannot be measured accurately by a platinum resistance thermometer?
question_answer11) Why is a constant volume gas thermo- meter preferred as a standard thermometer than a constant pressure gas thermometer?
question_answer12) A mercury thermometer is transferred from melting ice to a hot liquid. The mercury rises 0.9 of the distance between lower and upper fixed points. What is the temperature of the liquid in\[{}^\circ \mathbf{C}\]? What in \[{}^\circ \mathbf{F}\]?
question_answer13) The readings of air thermometer at\[~\mathbf{0}{}^\circ \mathbf{C}\] and \[\mathbf{100}{}^\circ \text{ }\mathbf{C}\] are \[\mathbf{50}\text{ }\mathbf{cm}\] and \[\mathbf{75}\text{ }\mathbf{cm}\] of mercury column respectively. What is the temperature at which its reading is \[\mathbf{80}\text{ }\mathbf{cm}\] of Hg column?
question_answer14) Two bodies at different temperatures \[{{T}_{1}}\] and \[{{T}_{2}}\] , if brought in thermal contact do not necessarily settle at the mean temperature \[({{T}_{1}}+{{T}_{2}})/2.\] Why?
question_answer15) A body at higher temperature contains more heat, comment.
question_answer16) Two hollow glass balls are connected by a tube, which has a pellet of mercury in the middle. Can the temperature of the surrounding air be determined from the position of the drop?
question_answer17) Do all solids expand on heating? If not, give an example.
question_answer18) Why does a solid expand on heating?
question_answer19) Is the temperature coefficient always positive?
question_answer20) The diameters of steel rods A and B having the same length are 2 cm and 4 cm respectively. They are heated through \[\mathbf{100}{}^\circ \text{ }\mathbf{C}\]. What is the ratio of increase of length of A to that of B?
question_answer21) The difference between lengths of a certain brass rod and that of a steel rod is claimed to be constant at all temperatures. Is this possible?
question_answer22) Why a small gap is left between the iron rails of railway tracks?
question_answer23) Why are loops provided in long metal pipes used for carrying oil and any other liquid over long distances?
question_answer24) Pendulum clocks generally run fast in winter and slow in summer. Why?
question_answer25) Why is invar used in making a clock pendulum?
question_answer26) Why must telephone or power lines necessarily slag a little?
question_answer27) A brass disc fits snugly in a hole in a steel plate. Should we heat or cool the system to loosen the disc from the hole?
question_answer28) A tightened glass stopper can be taken out easily by pouring hot water around the neck of the bottle. Why?
question_answer29) A long cylindrical vessel having linear coefficient of expansion \[\alpha \] is filled with a liquid up to a certain level. On heating, it is observed that the length of the liquid in the cylinder remains the same. What is the volume coefficient of expansion of the liquid?
question_answer30) Thick bottomed drinking glasses frequently crack if hot water is poured into them. Why?
question_answer31) Two identical rectangular strips of copper, and the other of steel are riveted to form a bimetallic strip. What will happen on heating?
question_answer32) Why iron rims are heated red hot before being put on the cart wheels?
question_answer33) In riveting boiler plates, red hot rivets are used. Why?
question_answer34) How does the diameter of the opening in the cast iron plate of a kitchen stove change, when the stove is heated?
question_answer35) A metal ball is heated through a certain temperature. Out of mass, radius, surface area and volume, which will undergo largest percentage increase and which one the least?
question_answer36) Explain why a beaker filled with water at \[\mathbf{4}{}^\circ \mathbf{C}\] overflows if the temperature is decreased or increased?
question_answer37) A block of wood is floating on water at \[\mathbf{0}{}^\circ \mathbf{C}\] with a certain volume V above the level of water. The temperature of water is gradually increased from \[\mathbf{0}{}^\circ \mathbf{C}\] to\[\mathbf{8}{}^\circ \mathbf{C}\]. How does the volume V change with the change of temperature?
question_answer38) Is \[J\] a physical quantity?
question_answer39) Why is \[J\] called a conversion factor?
question_answer40) A thermos bottle containing water is vigorously shaken. What will be the effect on the temperature of water?
question_answer41) When we rub our hands, they are warmed but only to a certain maximum temperature. Why?
question_answer42) There is a slight temperature difference between the water fall at the top and the bottom. Why?
question_answer43) Why do the brake drums of a car get heated, when the car moves down a hill at a constant speed?
question_answer44) Can a given amount of mechanical energy be completely converted into heat?
question_answer45) A match stick can be lighted by rubbing it against a rough surface. Why?
question_answer46) If an electric fan be switched in a closed room, will the air of the room be cooled? If not, why do we feel cold?
question_answer47) Give an example of a system in which no heat is transferred to or from a system but the temperature of the system changes.
question_answer48) What is the difference between the specific heat and the molar specific heat?
question_answer49) Why water is preferred to any other liquid in the hot water bottles?
question_answer50) The coolant used in a nuclear reactor should have high specific heat. Why?
question_answer51) Why juice bottles are placed under water in the cold countries?
question_answer52) Why is water used as an effective coolant?
question_answer53) What kind of thermal conductivity and specific heat requirements would you specify for cooking utensils?
question_answer54) Why do the metal utensils have wooden handles?
question_answer55) Why birds are often seen to swell their feathers in winter?
question_answer56) Why an ice box is constructed with a double wall?
question_answer57) Why are two thin blankets are warmer than a single blanket of double the thickness?
question_answer58) A squirred wraps its bushy tail round its body during its winter sleep. Why?
question_answer59) Calorimeters are made of metals not glass. Why?
question_answer60) When we step barefoot into an office with a marble floor, we feel cold. Why?
question_answer61) Why we can easily boil water in a paper cup?
question_answer62) A piece of paper wrapped tightly on a wooden rod is observed to get charred quickly when held over a flame as compared to a similar piece of paper when wrapped on a brass rod. Explain why.
question_answer63) A piece of wire gauze is placed over the Bunsen burner. If the gas is turned on below the gauge, will the flame go above the gauge?
question_answer64) Woolen clothes are worn in winter. Why?
question_answer65) Why do we use copper gauze in Davy's safety lamp?
question_answer66) Place a safety pin on a sheet of paper. Hold the sheet over a burning candle, until the paper becomes yellow and charr. On removing the pin, its white trace is observed on the paper. Why?
question_answer67) Stainless steel cooking pans are preferred with extra copper bottom. Why?
question_answer68) If a drop of water falls on a very hot iron, it does not evaporate for a long time. Give reason.
question_answer69) Pieces of copper and glass are heated to the same temperature. Why does the piece of copper feel hotter on touching?
question_answer70) Usually a good conductor of heat is a good conductor of electricity also. Give reason.
question_answer71) Why do electrons in insulators not contribute towards its thermal conductivity?
question_answer72) Why felt rather than air is employed for thermal insulation?
question_answer73) If air is poor conductor of heat, why do we not feel warm without clothes?
question_answer74) Why small holes are provided at the bottom of the chimney of the lamp?
question_answer75) Why rooms are provided with the ventilators near the roof?
question_answer76) Why it is much hotter above a fire than by its side?
question_answer77) Why snow is a better heat insulator than ice?
question_answer78) Can we boil water inside an earth satellite?
question_answer79) Water is heated from below. Why?
question_answer80) Suppose you want to cool your drink. Should you keep ice cubes floating on the top or should you arrange to keep the ice cubes at the bottom?
question_answer81) Why are the cooling coils fitted near the ceiling of a refrigerator?
question_answer82) After some time of the switching on an electric heater, the temperature of the heater becomes constant although current remains continuously flowing in it, why so?
question_answer83) The earth constantly receives heat radiation from the sun and gets warmed up. Why does the earth not get as hoi as the sun?
question_answer84) Why do animals curl into a ball, when they feel very cold?
question_answer85) Two thermos flasks are of the same height and same capacity. One has a circular cross section while the other has a square cross-section. Which of the two is better?
question_answer86) Why a body with large reflectivity is a poor emitter?
question_answer87) Why does a piece of red glass when heated and taken out glow with green light?
question_answer88) Two stars radiate maximum energy at wavelengths \[\mathbf{3}\mathbf{.6\times 1}{{\mathbf{0}}^{\mathbf{-7}}}\mathbf{m}\]and \[\mathbf{4}\mathbf{.8\times 1}{{\mathbf{0}}^{\mathbf{-7}}}\mathbf{m}\] respectively. What is the ratio of their temperatures?
question_answer89) If all the objects radiate electromagnetic energy, why do not the objects around us in everyday life become colder and colder?
question_answer90) Is it necessary that all black coloured objects should be considered black bodies?
question_answer91) Why are clear nights colder than cloudy nights?
question_answer92) White clothes are more comfortable in summer while colourful clothes are more comfortable in winter. Why?
question_answer93) Explain why cooking utensils are often blackened at the bottom and polished at the top.
question_answer94) Gasoline tanks are generally painted with aluminium paint. Why?
question_answer95) A hole in the cavity of a radiator is a black body. Why?
question_answer96) Why is there the word displacement in Wien's displacement law?
question_answer97) Black body radiation is white. Comment.
question_answer98) Which object will cool faster when kept in open air, the one at \[\mathbf{300}{}^\circ \text{ }\mathbf{C}\] or the one at\[\mathbf{100}{}^\circ \text{ }\mathbf{C}\]? Why?
question_answer99) In what respect is the thermal radiation different from light?
question_answer100) What is critical temperature?
question_answer101) Can a gas be liquified at any temperature by the increase of pressure alone?
question_answer102) What is the effect of pressure on melting point of a solid?
question_answer103) How does the boiling point of water change with pressure?
question_answer104) What is the temperature above which steam will not condense to water even if it is compressed (isothermally) to very large pressure?
question_answer105) What is the significance of negative slope of ice line of water?
question_answer106) Are the relative amounts of ice, water and vapour fixed at the triple point water?
question_answer107) What happens if water vapour at a pressure of \[\mathbf{0}.\mathbf{004}\text{ }\mathbf{atm}\] is cooled to\[\mathbf{0}{}^\circ \mathbf{C}\]?
question_answer108) Water exists in liquid phase at \[\mathbf{30}{}^\circ \mathbf{C}\] at 1 atmospheric pressure. How would you convert this water to vapour form without increasing its temperature?
question_answer109) What are the critical temperature and pressure for\[\mathbf{C}{{\mathbf{O}}_{\mathbf{2}}}\]? What is their significance?
question_answer110) Ice of \[{{\mathbf{0}}^{\circ }}\] is converted into steam at 100° C. State the isothermal changes in the process.
question_answer111) Explain why a new quilt is warmer than an old one.
question_answer112) Give reasons why water is considered unsuitable for use in thermometers.
question_answer113) Give four reasons why is mercury used in thermometers.
question_answer114) Give reasons why is a platinum wire used in a resistance thermometer.
question_answer115) Give some merits of gas thermometers over those of mercury thermometers.
question_answer116) Name the suitable thermometers to measure the following temperatures: - \[\mathbf{80}{}^\circ \text{ }\mathbf{C},\]\[\text{ }\mathbf{60}{}^\circ \text{ }\mathbf{C},\] \[\text{ }\mathbf{250}{}^\circ \text{ }\mathbf{C},\text{ }\mathbf{780}{}^\circ \text{ }\mathbf{C},\text{ }\mathbf{2000}{}^\circ \text{ }\mathbf{C}\]
question_answer117) Suggest suitable methods for measuring the temperature (i) surface of the sun, (ii) surface of the earth, (iii) an insect, and (iv) liquid helium.
question_answer118) Two large holes are cut in a metal sheet. If the sheet is heated, how will the diameters of the holes change?
question_answer119) In problem 7, will the distance between the two holes increase or decrease on heating?
question_answer120) There are two spheres of same radius and material at same temperature but one being solid while the other hollow. Which sphere will expand more if (i) they are heated to the same temperature (ii) same amount of heat is given to each of them?
question_answer121) Two bodies of specific heats \[{{c}_{1}}\] and \[{{c}_{2}}\] having same heat capacities are combined to form a single composite body. What is the specific heat of the composite body?
question_answer122) Two rods A and B are of equal length. Each rod has its ends at temperatures \[{{T}_{1}}\] and \[{{T}_{2}}\] . What is the condition that will ensure equal rates of flow of heat through the rods A and B?
question_answer123) Two vessels of different materials are identical in size and wall-thickness. They are filled with equal quantities of ice at\[\mathbf{0}{}^\circ \text{ }\mathbf{C}\]. If the ice melts completely in 10 and 25 minutes respectively, compare the coefficients of thermal conductivity of the materials of the vessels.
question_answer124) Two vessels A and B of different materials but having identical shape, size and wall- thickness are filled with ice and kept at the same place. Ice melts at the rate of \[\mathbf{100 g mi}{{\mathbf{n}}^{\mathbf{-}}}^{\mathbf{1}}\] and \[\mathbf{150 g mi}{{\mathbf{n}}^{\mathbf{-}}}^{\mathbf{1}}\] in A and B respectively. Assuming that heat enters the vessels through the walls only, calculate the ratio of thermal conductivities of their materials.
question_answer125) Water in a closed tube is heated with one arm placed vertically above an arc lamp. Water will begin to circulate along the tube in a counterclockwise direction. Is this true or false?
question_answer126) 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\[\mathbf{200}{}^\circ \mathbf{C}\]. Which of these objects will cool fastest and which one slowest when left in air at room temperature? Give reasons.
question_answer127) There are two rods of the same metal, same length, same area of cross-section, but one of square cross-section and the other of circular cross- section. One end of each is kept immersed in steam. After the steady state is reached, the other ends of the rods are touched. Which one will be hotter? Give reason.
question_answer128) A solid sphere of copper of radius R and a hollow sphere of the same material of inner radius r and outer radius R are heated to the same temperature and allowed to cool in the same environment. Which of them starts cooling faster?
question_answer129) On a hot day, a car is left in sunlight with all the windows closed. After some time, it is found that the inside of the car is considerably warmer than the air outside. Explain, why.
question_answer130) How does tea in a thermos flask remain hot for a long time?
question_answer131) Distinguish between conduction, convection and radiation.
question_answer132) A blackened platinum wire, when gradually heated, first appears dull red, then blue and finally white. Explain why.
question_answer133) In a coal fire, the pockets formed by coals appear brighter than the coals themselves. Is the temperature of such a pocket higher than the surface temperature of a glowing coal?
question_answer134) Answer the following questions : (a) A vessel with a movable piston maintained at a constant temperature by a thermostat contains a certain amount of liquid in equilibrium with its vapour. Does this vapour obey Boyle's law? In other words, what happens when the volume of vapour is decreased? Does the vapour pressure increase? (b) What is meant by 'superheated water' and 'super cooled vapour'? Do these states of water lie on its P-V-T surface? Give some practical applications of these states of water.
question_answer135) A fat man is used to consuming about worth of food everyday. His food contains of butter plus a plate of sweets everyday, besides items which provide him with other nutrients (proteins, vitamins, minerals, etc.) in addition to fats and carbohydrates. The caloric value of 10 g of butter is and that of a plate of sweets is of average .What dietary strategy should he adopt to cut down his calories to about per day? Assume the man cannot resist eating the full plate of sweets once it is offered to him!
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