## THERMAL PROPERTIES OF MATTER QUIZ-16

JEE Advanced Physics Syllabus can be referred by the IIT aspirants to get a detailed list of all topics that are important in cracking the entrance examination. JEE Advanced syllabus for Physics has been designed in such a way that it offers very practical and application-based learning to further make it easier for students to understand every concept or topic by correlating it with day-to-day experiences. In comparison to the other two subjects, the syllabus of JEE Advanced for physics is developed in such a way so as to test the deep understanding and application of concepts.

Q151. A sphere and a cube of same material and same total surface area are placed in the same evacuated space turn by turn after they are heated to the same temperature. Find the ratio of their rates of cooling in the enclosure
•  √(Ï€/6):1
•  √(Ï€/3):1
•  Ï€/√6:1
•  Ï€/√3:1
Solution

Q152. Span of a bridge is 2.4 km. At 30°C a cable along the span sags by 0.5 km. Taking Î±=12×10^(-6)/°C, change in length of cable for a change in temperature from 10°C to 42°C is
•  9.9 m
•  0.099 m
•  0.99 m
•  0.4 km
Solution

Q153. Two plates identical in size, one of black and rough surface (B_1) and the other smooth and polished (A_2) are interconnected by a thin horizontal pipe with a mercury pellet at the centre. Two more plates A_1(identical to A_2) and B_2(identical to B_1) are heated to the same temperature and placed closed to the plates B_1, and A_2 as shown in Figure. The mercury pellet
•   Moves to the right
•  Moves to the left
•  Remains stationary
•  Starts oscillating left and right
Solution
153 (c) Smooth and polished plates are poor radiators of heat. Hence, heat coming out from A small, even though B being a black and rough plate is a good absorber. Effictively the heat coming to the left of pellet P is small Black and rough plates are good radiators of heat. Hence, plate B_2 radiates heat to a satisfactory level; however, plate A_2, being smooth and polisher, is a bad absorber. Effictively, the heat coming to the right of P is also small

Q154. The coefficient of thermal conductivity of copper, mercury and glass are K_c,K_m and K_g, respectively, such that K_c>K_m>K_g. If the same quantity of heat is to flow per second per unit area of each and corresponding temperature gradients are, X_c,X_m and X_g, respectively then
•  X_c=X_m=X_g
•  X_c>X_m>X_g
•  X_c
•  X_m
Solution

Q155. A solid copper cube of edges 1 cm is suspended in an evacuated enclosure. Its temperature is found to fall from 100°C to 90°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°C to 99°C will be approximately
•  25 s
•  50 s
•  200 s
•  400 s
Solution

Q156. Figure shows then graph of the temperature Î¸ of a section of a bar of length l, with distance x from the hot end, in the steady state for a metal rod polished with a poor thermal conductor on its lateral surface. Which is the correct graph?
•  a
•  b
• c
•  d
Solution

Q157. One end of a cooper rod of uniform cross section and length 1.5 m is kept in contact with ice and the other end with water at 100°C. At what point along its length should a temperature of 200°C be maintained so that in the steady state, the mass of ice melting be equal to that of the steam produced in same interval of time. Assume that the whole system is insulated from surroundings: [L_ice=80 cal⁄g,L_steam=540 cal/g ]
•  10.34 cm from the end at 100℃
•  10.34 mm from the end at 100℃
•  1.034 cm from the end at 100℃
•  1.034 m from the end at 100℃
Solution

Q158. A vessel is party filled with a liquid. Coefficients of cubical expansion of material of the vessel and liquid are Î³_V and Î³_L, respectively. If the system is heated, then volume unoccupied by the liquid will necessarily
•  Remain unchanged if Î³_V=Î³_L
•  Increase if Î³_V=Î³_L
•  decrease if Î³_V=Î³_L
•  None of the above
Solution
158 (b) Since the vessel is partly filled, volume of the vessel is greater than that of the liquid. When a body having volume V is heated through ∆Î¸, then increase in its volume is given by ∆V=V∙Î³∙∆Î¸ Since, Î³_V=Î³_L, therefore ∆V∝V. Hence, on heating expansion of vessel will be greater than that of liquid. It means unoccupied volume will necessarily increase. So, option (b) is correct

Q159. Latent heat of ice is 80cal/g. A man melts 60 g of ice by chewing in 1 min. His power is
•  4800 W
•  336 W
•  1.33 W
•  >0.75 W
Solution
159 (b) Work done by man = Heat absorbed by ice =mL=60×80=4800 cal=20160 J ∴ Power =W/t=20160/60=336 W

Q160. An iron rod of length 50 cm is joined at an end to an aluminum rod of length 100 cm. All measurements refer to 20°C. The coefficients of linear expansion of iron and aluminum are 12×10(-6)/°C and 24×10(-6)/°C, respectively. The average coefficient of expansion of composite system is
•  36×10(-6)/°C
•  12×10(-6)/°C
•  20×10(-6)/°C
• 48×10(-6)/°C
Solution

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