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Heat Transfer Physics - Heat Transfer

Rajasthan Board (RBSE) - STD 12 Science - Physics (Rajasthan - English Medium). 82 questions in this chapter.

Question types

Heat Transfer question types

82 questions across 6 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.

82
Questions
6
Question groups
5
Question types
Sample Questions

Heat Transfer questions

One sample from each question group in this chapter. Select any group above to see the full set with answer keys.

Q 1M.C.Q (1 Marks)1 Mark
A heated body emits radiation which has maximum intensity near the frequency $v_0$. The emissivity of the material is $0.5$. If the absolute temperature of the body is doubled:
  • A
    The maximum intensity of radiation will be near the frequency $2v_0$
  • B
    The maximum intensity of radiation will be near the frequency $\frac{\text{v}_0}{2}$
  • ✓
    The total energy emitted will increase by a factor of $16.$
  • D
    The total energy emitted will increase by a factor of $8.$

Answer: C.

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Q 2M.C.Q (1 Marks)1 Mark
One end of a metal rod is dipped in boiling water and the other is dipped in melting ice:
  1. All parts of the rod are in thermal equilibrium with each other.
  2. We can assign a temperature to the rod.
  3. We can assign a temperature to the rod after steady state is reached.
  4. The state of the rod does not change after steady state is reached.
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Q 3M.C.Q (1 Marks)1 Mark
In a room containing air, heat can go from one place to another:
  1. By conduction only.
  2. By convection only.
  3. By radiation only.
  4. By all the three modes.
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Q 4M.C.Q (1 Marks)1 Mark
A hot liquid is kept in a big room. Its temperature is plotted as a function of time. Which of the following curves may represent the plot?
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Q 61 Marks Question1 Mark
Assume that the total surface area of a human body is $1.6m^2$ and that it radiates like an ideal radiator. Calculate the amount of energy radiated per second by the body if the body temperature is $37^\circ C.$ Stefan constant $\sigma$ is $6.0 \times 10^{-8}Wm^{-2}K^{-4}.$
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Q 71 Marks Question1 Mark
Standing in the sun is more pleasant on a cold winter day than standing in shade. Is the temperature of air in the sun considerably higher than that of the air in shade?
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Q 92 Marks Questions2 Marks
On a cold winter night you are asked to sit on a chair. Would you like to choose a metal chair or a wooden chair? Both are kept in the same lawn and are at the same temperature.
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Q 122 Marks Questions2 Marks
Calculate the amount of heat radiated per second by a body of surface area $12\ cm^2$ kept in thermal equilibrium in a room at temperature $20^\circ C.$ The emissivity of the surface $= 0.80$ and $\sigma=6.0\times10^{-8}\text{Wm}^{-2}\text{K}^{-4}.$
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Q 132 Marks Questions2 Marks
A copper sphere is suspended in an evacuated chamber maintained at 300K. The sphere is maintained at a constant temperature of 500K by heating it electrically. A total of 210W of electric power is needed to do it. When the surface of the copper sphere is completely blackened, 700W is needed to maintain the same temperature of the sphere. Calculate the emissivity of copper.
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Q 143 Marks Question3 Marks
One end of a rod of length 20cm is inserted in a furnace at 800K The sides of the rod are covered with an insulating material and the other end emits radiation like a blackbody. The temperature of this end is 750K in the steady state. The temperature of the surrounding air is 300K. Assuming radiation to be the only important mode of energy transfer between the surrounding and the open end of the rod, find the thermal conductivity of the rod. Stefan constant $\sigma=6.0\times10^{-8}\text{Wm}^{-2}\text{K}^{-4}.$
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Q 153 Marks Question3 Marks
Four identical rods $AB, CD, CF$ and $DE$ are joined as shown in figure. The length, cross$-$sectional area and thermal conductivity of each rod are $l, A$ and $K$ respectively. The ends $A, E$ and $F$ are maintained at temperatures $T_1, T_2$ and $T_3$ respectively. Assuming no loss of heat to the atmosphere, find the temperature at $B.$​​​​​​​
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Q 173 Marks Question3 Marks
A cylindrical rod of length $50\ cm$ and cross sectional area $1\ cm^2$ is fitted between a large ice chamber at $0^\circ C$ and an evacuated chamber maintained at $27^\circ C$ as shown in figure. Only small portions of the rod are inside the chambers and the rest is thermally insulated from the surrounding. The cross section going into the evacuated chamber is blackened so that it completely absorbs any radiation falling on it. The temperature of the blackened end is $17^\circ C$ when steady state is reached. Stefan constant $\sigma=6\times10^{-8}\text{W/m}^{-2}\text{K}^{-4}.$ Find the thermal conductivity of the material of the rod.
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Q 183 Marks Question3 Marks
A uniform slab of dimension $10\ cm \times 10\ cm \times 1\ cm$ is kept between two heat reservoirs at temperatures $10^\circ C$ and $90^\circ C.$ The larger surface areas touch the reservoirs. The thermal conductivity of the material is $0.80\text{wm}^{-1}{^{\circ}}\text{C}^{-1}.$ Find the amount of heat flowing through the slab per minute.
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Q 194 Marks Questions4 Marks
Suppose the bent part of the frame of the previous problem has a thermal conductivity of $780Js^{-1}m^{-1^\circ }C^{-1}$ whereas it is $390Js^{-1}m^{-1^\circ }C^{-1}$ for the straight part. Calculate the ratio of the rate of heat flow through the bent part to the rate of heat flow through the straight part.
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Q 204 Marks Questions4 Marks
The three rods shown in figure, have identical geometrical dimensions. Heat flows from the hot end at a rate of $40$ Win the arrangement $(a)$ Find the rates of heat flow when the rods are joined as in arrangement $(b)$ and in $(c)$ Thermal conductivities of aluminium and copper are $200Wm^{-1^\circ }C^{-1}$ and $400Wm^{-1^\circ }C^{-1}$ respectively.
  1.  
  1.  
  1.  
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Q 214 Marks Questions4 Marks
On a winter day when the atmospheric temperature drops to $-10^\circ C$, ice forms on the surface of a lake.
  1. Calculate the rate of increase of thickness of the ice when $10\ cm$ of ice is already formed.
  2. Calculate the total time taken in forming $10\ cm$ of ice. Assume that the temperature of the entire water reaches $0^\circ C$ before the ice starts forming. Density of water $= 1000\ kgm^{-3}$, latent heat of fusion of ice $=3.36\times10^5\text{Jkg}^{-1}$ and thermal conductivity of ice $=1.7\text{Wm}^{-1}{^{\circ}}\text{C}^{-1}.$ Neglect the expansion of water on freezing.
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Q 234 Marks Questions4 Marks
Consider the situation shown in figure. The frame is made of the same material and has a uniform cross$-$sectional area everywhere. Calculate the amount of heat flowing per second through a cross section of the bent part if the total heat taken out per second from the end at $100^\circ C$ is $130J.$​​​​​​​
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Q 245 Marks Questions5 Marks
Steam at $120^\circ C$ is continuously passed through a $50\ cm$ long rubber tube of inner and outer radii $1.0\ cm$ and $1.2\ cm.$ The room temperature is $30^\circ C.$ Calculate the rate of heat flow through the walls of the tube. Thermal conductivity of rubber $= 0.15Js^{-1}m^{-1\ \circ}C^{-1}.$
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Q 255 Marks Questions5 Marks
Seven rods $\ce{A, B, C, D, E, F}$ and $\ce{G}$ are joined as shown in figure. All the rods have equal cross$-$sectional area $A$ and length $l.$ The thermal conductivities of the rods are $\ce{K_A = K_c = K_0, K_B = K_D = 2K_0, K_{E }= 3K_{0,} K_F = 4K_0,}$ and $K_G = 5K_0.$ The rod $E$ is kept at a constant temperature $T_2$ and the rod $\ce{G}$ is kept at a constant temperature $\ce{T_2(T_2 > T_1).}$
  1. Show that the rod $\ce{F}$ has a uniform temperature $\text{T}=\frac{(\text{T}_1+2\text{T}_2)}{3}.$
  2. Find the rate of heat flowing from the source which maintains the temperature $\ce{T_2.}$
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Q 265 Marks Questions5 Marks
A calorimeter contains $50g$ of water at $50^\circ C$. The temperature falls to $45^\circ C$ in $10$ minutes. When the calorimeter contains $100g$ of water·at $50^\circ 0$, it takes $18$ minutes for the temperature to become $45^\circ C$. Find the water equivalent of the calorimeter.
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Q 275 Marks Questions5 Marks
An icebox almost completely filled with ice at $0^\circ C$ is dipped into a large volume of water at $20^\circ C.$ The box has walls of surface area $2400\ cm^2,$ thickness $2.0mm$ and thermal conductivity $0.06\text{Wm}^{-1}{^{\circ}}\text{C}^{-1}.$ Calculate the rate at which the ice melts in the box. Latent heat of fusion of ice $= 3.4\times10^5\text{Jkg}^{-1}.$
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Q 285 Marks Questions5 Marks
A solid aluminium sphere and a solid copper sphere of twice the radius are heated to the same temperature and are allowed to cool under identical surrounding temperatures. Assume that the emissivity of both the spheres is the same. Find the ratio of:
  1. The rate of heat loss from the aluminium sphere to the rate of heat loss from the copper sphere.
  2. The rate of fall of temperature of the aluminium sphere to the rate of fall of temperature of the copper sphere. The specific heat capacity of aluminium $= 900Jkg^{-1^\circ }C^{-1}$ and that of copper $= 390Jkg^{-1^\circ }C^{-1}$. The density of copper $= 3.4$ times the density of aluminium.
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