Three identical heat conducting rods are connected in series as shown in the figure. The rods on the sides have thermal conductivity \(2K\) while that in the middle has thermal conductivity \(K\) . The left end of the combination is maintained at temperature \(3T\) and the right end at \(T.\) The rods are thermally insulated from outside. In the steady state, temperature at the left junction is \(T_1\) and that at the right junction is \(T_2\) . The ratio \(\dfrac{T_1}{T_2}\) is:
Question 2.
Two rods, one made of copper and the other made of steel, of the same length and same cross-sectional area are joined together. The thermal conductivity of copper and steel are \(385~\text{Js}^{-1}\text{K}^{-1}\text{m}^{-1}\) and \(50~\text{Js}^{-1}\text{K}^{-1}\text{m}^{-1}\) respectively. The free ends of copper and steel are held at \(100^\circ \text{C}\) and \(0^\circ \text{C}\) respectively. The temperature at the junction is, nearly:
Question 3.
The quantities of heat required to raise the temperature of two solid copper spheres of radii \(r_1\) and \(r_2\)\((r_1=1.5~r_2)\) through \(1~\text{K}\) are in the ratio:
Question 4.
A deep rectangular pond of surface area \(A\), containing water (density = \(\rho,\) specific heat capacity = \(s\)), is located in a region where the outside air temperature is at a steady value of \(-26^{\circ}\text{C}\). The thickness of the ice layer in this pond at a certain instant is \(x\). Taking the thermal conductivity of ice as \(k\), and its specific latent heat of fusion as \(L\), the rate of increase of the thickness of the ice layer, at this instant, would be given by:
Question 5.
Two rods \(A\) and \(B\) of different materials are welded together as shown in the figure. Their thermal conductivities are \(K_1\) and \(K_2.\) The thermal conductivity of the composite rod will be:
Question 6.
The two ends of a metal rod are maintained at temperatures \(100~^\circ\text{C}\) and \(110~^\circ\text{C}.\) The rate of heat flow in the rod is found to be \(4.0\) J/s. If the ends are maintained at temperatures \(200~^\circ \text{C}\) and \(210 ~^\circ \text{C},\) the rate of heat flow will be:
Question 7.
A slab of stone with an area \(0.36~\text{m}^{2}\) and thickness of \(0.1~\text{m}\) is exposed on the lower surface to steam at \(100^\circ\text{C}.\) A block of ice at \(0^{\circ}\text{C}\) rests on the upper surface of the slab. In one hour \(4.8~\text{kg}\) of ice is melted. The thermal conductivity of the slab will be:
(Given latent heat of fusion of ice \(= 3.36\times10^{5}~\text{JKg}^{-1}\))
Question 8.
A cylindrical metallic rod in thermal contact with two reservoirs of heat at its two ends conducts an amount of heat Q in time t. The metallic rod is melted and the material is formed into a rod of half the radius of the original rod. What is the amount of heat conducted by the new rod when placed in thermal contact with the two reservoirs at the same time?
Question 9.
The two ends of a rod of length L and a uniform cross-sectional area A are kept at two temperatures T1 and T2 (T1> T2). The rate of heat transfer through the rod in a steady state is given by:
Question 10.
Which of the following circular rods, (given radius \(r\) and length \(l\)) each made of the same material and whose ends are maintained at the same temperature will conduct the most heat:
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Question 1.
Consider a compound slab consisting of two different materials having equal thicknesses and thermal conductivities K and 2K, respectively. The equivalent thermal conductivity of the slab will be:
Question 2.
Consider two rods of the same length and different specific heats \((S_1,S_2)\) conductivities \((K_1,K_2)\) and area of cross-sections \((A_1,A_2)\) and both having temperature \(T_1\) and \(T_2\) at their ends. If the rate of loss of heat due to conduction is equal, then:
Question 3.
A cylindrical rod has temperatures at its ends. The rate of flow of heat is cal/sec. If all the linear dimensions are doubled while keeping the temperature constant, then the rate of flow of heat will be:
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