JEE Main & Advanced Physics Transmission of Heat Question Bank

done Critical Thinking Total Questions - 37

• question_answer1)
  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                                                                   [UPSEAT 2002]
  A)
             2 : p done clear
  B)
             1 : 2 done clear
  C)
             p : 2 done clear
  D)
             3 : 2 done clear
  View Solution play_arrow

• question_answer2)
  A wall is made up of two layers A and B. The thickness of the two layers is the same, but materials are different. The thermal conductivity of A is double than that of B. In thermal equilibrium the temperature difference between the two ends is \[{{36}^{o}}C\]. Then the difference of temperature at the two surfaces of A will be [IIT 1980; CPMT 1991; BHU 1997; MP PET 1996, 99; DPMT 2000]
  A)
             \[{{6}^{o}}C\]                       done clear
  B)
             \[{{12}^{o}}C\] done clear
  C)
             \[{{18}^{o}}C\]                     done clear
  D)
             \[{{24}^{o}}C\] done clear
  View Solution play_arrow

• question_answer3)
  Ice starts forming in lake with water at \[{{0}^{o}}C\] and when the atmospheric temperature is \[-{{10}^{o}}C\]. If the time taken for 1 cm of ice be 7 hours, then the time taken for the thickness of ice to change from 1 cm to 2 cm is [NCERT 1971; MP PMT/PET 1988; UPSEAT 1996]
  A)
             7 hours                                    done clear
  B)
             14 hours done clear
  C)
             Less than 7 hours                done clear
  D)
             More than 7 hours done clear
  View Solution play_arrow

• question_answer4)
  A cylinder of radius R made of a material of thermal conductivity \[{{K}_{1}}\] is surrounded by a cylindrical shell of inner radius R and outer radius 2R made of material of thermal conductivity\[{{K}_{2}}\]. The two ends of the 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                      [IIT 1988; MP PMT 1994, 97; SCRA 1998]
  A)
             \[{{K}_{1}}+{{K}_{2}}\]      done clear
  B)
             \[\frac{{{K}_{1}}{{K}_{2}}}{{{K}_{1}}+{{K}_{2}}}\] done clear
  C)
             \[\frac{{{K}_{1}}+3{{K}_{2}}}{4}\]                                    done clear
  D)
             \[\frac{3{{K}_{1}}+{{K}_{2}}}{4}\] done clear
  View Solution play_arrow

• question_answer5)
  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 \[{{0}^{o}}C\] and \[{{90}^{o}}C\] respectively. The temperature of the junction of the three rods will be [IIT-JEE (Screening) 2001]
  A)
             \[{{45}^{o}}C\] done clear
  B)
             \[{{60}^{o}}C\] done clear
  C)
             \[{{30}^{o}}C\] done clear
  D)
             \[{{20}^{o}}C\] done clear
  View Solution play_arrow

• question_answer6)
  A room is maintained at \[{{20}^{o}}C\] by a heater of resistance 20 ohm connected to 200 volt mains. The temperature is uniform throughout the room and heat is transmitted through a glass window of area \[1{{m}^{2}}\] and thickness 0.2 cm. What will be the temperature outside? Given that thermal conductivity K for glass is \[320\ kcal/{{m}^{2}}\ min\] and J = 4.2 J/cal [IIT 1978]
  A)
             \[{{15.24}^{o}}C\]               done clear
  B)
             15.00°C done clear
  C)
             \[{{24.15}^{o}}C\]               done clear
  D)
             None of the above done clear
  View Solution play_arrow

• question_answer7)
  There is formation of layer of snow \[x\,cm\] thick on water, when the temperature of air is \[-{{\theta }^{o}}C\] (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
  A)
             \[\frac{(x+y)(x-y)\rho L}{2k\theta }\]                            done clear
  B)
             \[\frac{(x-y)\rho L}{2k\theta }\] done clear
  C)
             \[\frac{(x+y)(x-y)\rho L}{k\theta }\]                              done clear
  D)
             \[\frac{(x-y)\rho Lk}{2\theta }\] done clear
  View Solution play_arrow

• question_answer8)
  A composite metal bar of uniform section is made up of length 25 cm of copper, 10 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 \[{{100}^{o}}C\] and the aluminium end at \[{{0}^{o}}C\]. The whole rod is covered with belt so that there is no heat loss occurs at the sides. If \[{{K}_{\text{Cu}}}=2{{K}_{Al}}\] and \[{{K}_{Al}}=3{{K}_{\text{Ni}}}\], then what will be the temperatures of \[Cu-Ni\] and \[Ni-Al\] junctions respectively
  A)
             \[{{23.33}^{o}}C\] and \[A\]   done clear
  B)
             \[{{83.33}^{o}}C\] and \[{{20}^{o}}C\] done clear
  C)
             \[{{50}^{o}}C\] and \[{{30}^{o}}C\]                                 done clear
  D)
             \[{{30}^{o}}C\] and \[{{50}^{o}}C\] done clear
  View Solution play_arrow

• question_answer9)
  Three rods of identical area of cross-section and made from the same metal form the sides of an isosceles triangle \[ABC\], right angled at \[B\]. The points \[A\] and \[B\] are maintained at temperatures \[T\] and \[\sqrt{2}T\] respectively. In the steady state the temperature of the point C is \[{{T}_{C}}\]. Assuming that only heat conduction takes place, \[\frac{{{T}_{C}}}{T}\] is equal to        [IIT 1995]
  A)
             \[\frac{1}{(\sqrt{2}+1)}\] done clear
  B)
             \[\frac{3}{(\sqrt{2}+1)}\] done clear
  C)
             \[\frac{1}{2(\sqrt{2}-1)}\]       done clear
  D)
             \[\frac{1}{\sqrt{3}(\sqrt{2}-1)}\] done clear
  View Solution play_arrow

• question_answer10)
  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/cmsecoC. 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 [CPMT 1974, 78; MNR 1983]
  A)
             2.47 hr done clear
  B)
             4.27 hr done clear
  C)
             7.42 hr done clear
  D)
             4.72 hr done clear
  View Solution play_arrow

• question_answer11)
  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 1000°C. Which one of these will cool first[IIT 1972; MP PMT 1993; J & K CET 2000 MH CET 2000; UPSEAT 2001]
  A)
             Plate                                         done clear
  B)
              Sphere done clear
  C)
             Cube                                        done clear
  D)
              None of these done clear
  View Solution play_arrow

• question_answer12)
  Three rods of the same dimension have thermal conductivities 3K, 2K and K. They are arranged as shown in fig. Given below, with their ends at 100oC, 50oC and 20oC. The temperature of their junction is                        [UPSEAT 2002]
  A)
             \[{{60}^{o}}\]C done clear
  B)
             \[{{70}^{o}}\] C done clear
  C)
             50o C done clear
  D)
             35o C done clear
  View Solution play_arrow

• question_answer13)
  Two identical conducting rods are first connected independently to two vessels, one containing water at 100o C and the other containing ice at 0oC. In the 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 \[{{q}_{1}}/{{q}_{2}}\] is  [IIT-JEE (Screening) 2004]
  A)
             \[\frac{1}{2}\]                       done clear
  B)
             \[\frac{2}{1}\] done clear
  C)
             \[\frac{4}{1}\]                       done clear
  D)
             \[\frac{1}{4}\] done clear
  View Solution play_arrow

• question_answer14)
  A solid cube and a solid sphere of the same material have equal surface area. Both are at the same temperature \[{{120}^{o}}C\], then                [MP PET 1992, 96; MP PMT 2000]
  A)
             Both the cube and the sphere cool down at the same rate done clear
  B)
             The cube cools down faster than the sphere done clear
  C)
             The sphere cools down faster than the cube done clear
  D)
             Whichever is having more mass will cool down faster done clear
  View Solution play_arrow

• question_answer15)
  Two bodies \[A\]and \[B\] have thermal emissivities of 0.01 and 0.81 respectively. The outer surface areas of the two bodies are the same. The two bodies emit total radiant power at the same rate. The wavelength \[{{\lambda }_{B}}\] corresponding to maximum spectral radiancy in the radiation from \[B\] is shifted from the wavelength corresponding to maximum spectral radiancy in the radiation from \[A\], by \[1.00\mu m\]. If the temperature of \[A\] is \[5802\ K\]                                                                      [IIT 1994; DCE 1996]
  A)
             The temperature of \[B\] is \[1934\ K\] done clear
  B)
             \[{{\lambda }_{B}}=1.5\mu m\] done clear
  C)
             The temperature of \[B\] is \[11604\ K\] done clear
  D)
             The temperature of \[B\] is \[2901\ K\] done clear
  View Solution play_arrow

• question_answer16)
  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 \[{{U}_{1}}\], between \[999\ nm\] and \[1000\ nm\] is \[{{U}_{2}}\] and between \[1499\ nm\] and \[1500\ nm\] is \[{{U}_{3}}\]. The Wein's constant\[b=2.88\times {{10}^{6}}\ nm\,K\]. Then [IIT 1998]
  A)
             \[{{U}_{1}}=0\]                    done clear
  B)
             \[{{U}_{3}}=0\] done clear
  C)
             \[{{U}_{1}}>{{U}_{2}}\]    done clear
  D)
             \[{{U}_{2}}>{{U}_{1}}\] done clear
  View Solution play_arrow

• question_answer17)
  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                                                             [MP PMT 1997]
  A)
             16P done clear
  B)
             4P done clear
  C)
             2P   done clear
  D)
             P done clear
  View Solution play_arrow

• question_answer18)
  Three rods of same dimensions are arranged as shown in figure they have thermal conductivities \[{{K}_{1}},{{K}_{2}}\] and\[{{K}_{3}}\] 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 option is correct                [KCET 2001]
  A)
             \[{{K}_{3}}=\frac{1}{2}({{K}_{1}}+{{K}_{2}})\] done clear
  B)
             \[{{K}_{3}}={{K}_{1}}+{{K}_{2}}\] done clear
  C)
             \[{{K}_{3}}=\frac{{{K}_{1}}{{K}_{2}}}{{{K}_{1}}+{{K}_{2}}}\] done clear
  D)
             \[{{K}_{3}}=2({{K}_{1}}+{{K}_{2}})\] done clear
  View Solution play_arrow

• question_answer19)
  Two metallic spheres \[{{S}_{1}}\] and \[{{S}_{2}}\]are made of the same material and have identical surface finish. The mass of \[{{S}_{1}}\] is three times that of \[{{S}_{2}}\]. 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 ratio of the initial rate of cooling of \[{{S}_{1}}\] to that of \[{{S}_{2}}\] is                       [IIT 1995]
  A)
             \[1/3\]                                     done clear
  B)
             \[{{(1/3)}^{1/3}}\] done clear
  C)
             \[1/\sqrt{3}\]                        done clear
  D)
             \[\sqrt{3}/1\] done clear
  View Solution play_arrow

• question_answer20)
  Three discs A, B and C having radii 2m, 4m, and 6m 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 respectively [IIT-JEE (Screening) 2004]
  A)
             Qa is maximum                     done clear
  B)
             Qb is maximum done clear
  C)
             Qc is maximum                     done clear
  D)
             Qa = Qb = Qc done clear
  View Solution play_arrow

• question_answer21)
  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 is found to increase form \[{{20}^{o}}C\] to \[{{20.5}^{o}}C\]. If the absolute temperature of the black body is doubled and the experiment is repeated with the same quantity of water at \[{{20}^{o}}C\], the temperature of water will be [UPSEAT 2004]
  A)
             \[{{21}^{o}}C\]                     done clear
  B)
             \[{{22}^{o}}C\] done clear
  C)
             \[{{24}^{o}}C\]                     done clear
  D)
             \[{{28}^{o}}C\] done clear
  View Solution play_arrow

• question_answer22)
  A solid sphere and a hollow sphere of the same material and size are heated to the same temperature and allowed to cool in the same surroundings. If the temperature difference between each sphere and its surroundings is \[T\], then [Manipal MEE 1995]
  A)
             The hollow sphere will cool at a faster rate for all values of \[T\] done clear
  B)
             The solid sphere will cool at a faster rate for all values of \[T\] done clear
  C)
             Both spheres will cool at the same rate for all values of \[T\] done clear
  D)
             Both spheres will cool at the same rate only for small values of \[T\] done clear
  View Solution play_arrow

• question_answer23)
  A solid copper cube of edges \[1\ cm\] is suspended in an evacuated enclosure. Its temperature is found to fall from \[{{100}^{o}}C\] to \[{{99}^{o}}C\] 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 \[{{100}^{o}}C\] to \[{{99}^{o}}C\] will be approximately               [MP PMT 1997]
  A)
             \[25\ s\]                                  done clear
  B)
             \[50\ s\] done clear
  C)
             \[200\ s\]                                done clear
  D)
             \[400\ s\] done clear
  View Solution play_arrow

• question_answer24)
  A body initially at 80o C cools to 64o C in 5 minutes and to 52o C in 10 minutes. The temperature of the body after 15 minutes will be                                      [UPSEAT 2000; Pb. PET 2004]
  A)
             42.7 o C                                     done clear
  B)
             35 o C done clear
  C)
             47 o C                                        done clear
  D)
             40 o C done clear
  View Solution play_arrow

• question_answer25)
  A 5cm thick ice block is there on the surface of water in a lake. The temperature of air is ?10°C; how much time it will take to double the thickness of the block (L = 80 cal/g, Kicc = 0.004 Erg/s-k, dice = 0.92 g cm?3) [RPET 1998]
  A)
             1 hour                                      done clear
  B)
             191 hours done clear
  C)
             19.1 hours                              done clear
  D)
             1.91 hours done clear
  View Solution play_arrow

• question_answer26)
  Four identical rods of same material are joined end to end to form a square. If the temperature difference between the ends of a diagonal is \[{{100}^{o}}C\], then the temperature difference between the ends of other diagonal will be [MP PET 1989; RPMT 2002]
  A)
             \[{{0}^{o}}C\] done clear
  B)
             \[\frac{100}{l}{{\ }^{o}}C\]; where l is the length of each rod done clear
  C)
             \[\frac{100}{2l}{{\ }^{o}}C\] done clear
  D)
             \[{{100}^{o}}C\] done clear
  View Solution play_arrow

• question_answer27)
  A cylindrical rod with one end in a steam chamber and the other end in ice results in melting of 0.1gm 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 \[\frac{1}{4}\] that of first, the rate at which ice melts in \[gm/\sec \]will be                    [EAMCET 1987]
  A)
             3.2  done clear
  B)
             1.6 done clear
  C)
             0.2  done clear
  D)
             0.1 done clear
  View Solution play_arrow

• question_answer28)
  One end of a copper rod of length \[1.0\ m\] and area of cross-section \[{{10}^{-3}}\] is immersed in boiling water and the other end in ice. If the coefficient of thermal conductivity of copper is \[92\ cal/m\text{-}s{{\text{-}}^{o}}C\] and the latent heat of ice is \[8\times {{10}^{4}}cal/kg\], then the amount of ice which will melt in one minute is [MNR 1994]
  A)
             \[9.2\times {{10}^{-3}}kg\]     done clear
  B)
             \[8\times {{10}^{-3}}kg\] done clear
  C)
             \[6.9\times {{10}^{-3}}kg\]     done clear
  D)
             \[5.4\times {{10}^{-3}}kg\] done clear
  View Solution play_arrow

• question_answer29)
  An ice box used for keeping eatable cold has a total wall area of \[1\ metr{{e}^{2}}\] and a wall thickness of \[5.0cm\]. The thermal conductivity of the ice box is \[K=0.01\ joule/metre{{-}^{o}}C\]. It is filled with ice at \[{{0}^{o}}C\] along with eatables on a day when the temperature is 30°C. The latent heat of fusion of ice is \[334\times {{10}^{3}}joules/kg\]. The amount of ice melted in one day is (\[1day=86,400\ \sec onds\])                              [MP PMT 1995]
  A)
             \[776\ gms\]                         done clear
  B)
             \[7760\ gms\] done clear
  C)
             \[11520\ gms\]                     done clear
  D)
             \[1552\ gms\] done clear
  View Solution play_arrow

• question_answer30)
  Five rods of same dimensions are arranged as shown in the figure. They have thermal conductivities K1, K2, K3, K4 and K5. When points A and B are maintained at different temperatures, no heat flows through the central rod if [KCET 2002]
  A)
             \[{{K}_{1}}={{K}_{4}}\,\text{and}\,\ {{K}_{2}}={{K}_{3}}\] done clear
  B)
             \[{{K}_{1}}{{K}_{4}}={{K}_{2}}{{K}_{3}}\] done clear
  C)
             \[{{K}_{1}}{{K}_{2}}={{K}_{3}}{{K}_{4}}\] done clear
  D)
             \[\frac{{{K}_{1}}}{{{K}_{4}}}=\frac{{{K}_{2}}}{{{K}_{3}}}\] done clear
  View Solution play_arrow

• question_answer31)
  A hot metallic sphere of radius \[r\] radiates heat. It's rate of cooling is
  A)
             Independent of \[r\]         done clear
  B)
             Proportional to \[r\] done clear
  C)
             Proportional to \[{{r}^{2}}\]   done clear
  D)
             Proportional to \[1/r\] done clear
  View Solution play_arrow

• question_answer32)
  A solid copper sphere (density \[\rho \] and specific heat capacity c) of radius r at an initial temperature 200K is suspended inside a chamber whose walls are at almost 0K. The time required (in \[\mu \]s) for the temperature of the sphere to drop to 100 K is                                  [IIT-JEE 1991]
  A)
             \[\frac{72}{7}\frac{r\rho c}{\sigma }\]                                    done clear
  B)
             \[\frac{7}{72}\frac{r\rho c}{\sigma }\] done clear
  C)
             \[\frac{27}{7}\frac{r\rho c}{\sigma }\]                                    done clear
  D)
             \[\frac{7}{27}\frac{r\rho c}{\sigma }\] done clear
  View Solution play_arrow

• question_answer33)
  One end of a copper rod of uniform cross-section and of length 3.1 m is kept in contact with ice and the other end with water at 100°C. At what point along it's length should a temperature of 200°C be maintained so that in steady state, the mass of ice melting be equal to that of the steam produced in the same interval  of time. Assume that the whole system is insulated from the surroundings. Latent heat of fusion of ice and vaporisation of water are 80 cal/gm and 540 cal/gm respectively
  A)
             40 cm from 100°C end       done clear
  B)
             40 cm from 0°C end done clear
  C)
             125 cm from 100°C end     done clear
  D)
             125 cm from 0°C end done clear
  View Solution play_arrow

• question_answer34)
  A sphere and a cube of same material and same volume are heated upto same temperature and allowed to cool in the same surroundings. The ratio of the amounts of radiations emitted will be
  A)
             1 : 1                                           done clear
  B)
             \[\frac{4\pi }{3}\,\,:\,\,1\] done clear
  C)
             \[{{\left( \frac{\pi }{6} \right)}^{1/3}}:\,\,1\]                    done clear
  D)
             \[\frac{1}{2}\,{{\left( \frac{4\pi }{3} \right)}^{2/3}}:\,\,1\] done clear
  View Solution play_arrow

• question_answer35)
  The temperature of the two outer surfaces of a composite slab, consisting of two materials having coefficients of thermal conductivity K and 2K and thickness x and 4x, respectively are T2 and T1 (T2  > T1). The rate of heat transfer through the slab, in a steady state is \[\left( \frac{A({{T}_{2}}-{{T}_{1}})K}{x} \right)f\], with ¦ which equal to      [AIEEE 2004]
  A)
             1 done clear
  B)
             \[\frac{1}{2}\] done clear
  C)
             \[\frac{2}{3}\] done clear
  D)
             \[\frac{1}{3}\] done clear
  View Solution play_arrow

• question_answer36)
  The figure shows a system of two concentric spheres of radii r1 and r2 and kept at temperatures T1 and T2, respectively. The radial rate of flow of heat in a substance between the two concentric spheres is proportional to [AIEEE 2005]
  A)
             \[\frac{{{r}_{1}}\,{{r}_{2}}}{({{r}_{1}}-{{r}_{2}})}\] done clear
  B)
             \[({{r}_{2}}-{{r}_{1}})\] done clear
  C)
             \[({{r}_{2}}-{{r}_{1}})({{r}_{1}}\,{{r}_{2}})\] done clear
  D)
             In \[\left( \frac{{{r}_{2}}}{{{r}_{1}}} \right)\] done clear
  View Solution play_arrow

• question_answer37)
  Four rods of identical cross-sectional area and made from the same metal form the sides of square. The temperature of two diagonally opposite points and T and \[\sqrt{2}\]T respective in the steady state. Assuming that only heat conduction takes place, what will be the temperature difference between other two points                                       [BCECE 2005]
  A)
             \[\frac{\sqrt{2}+1}{2}T\]  done clear
  B)
             \[\frac{2}{\sqrt{2}+1}T\] done clear
  C)
             0     done clear
  D)
             None of these done clear
  View Solution play_arrow