A blackbody does not:
- AEmit radiation.
- BAbsorb radiation.
- CReflect radiation.
- ✓Refract radiation.
Answer: D.
View full solution →Question types
Heat Transfer. question types
79 questions across 6 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.
79
Questions
6
Question groups
5
Question types
01
M.C.Q (1 Marks)
13 Q→021 Marks Question
3 Q→032 Marks Questions
7 Q→043 Marks Question
17 Q→055 Marks Questions
33 Q→06Case study (4 Marks)
6 Q→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.
In a room containing air, heat can go from one place to another:
- ABy conduction only.
- BBy convection only.
- CBy radiation only.
- ✓By all the three modes.
Answer: D.
View full solution →The thermal conductivity of a rod depends on:
- ALength.
- BMass.
- CArea of cross section.
- ✓Material of the rod.
Answer: D.
View full solution →One end of a metal rod is kept in a furnace. In steady state, the temperature of the rod:
- AIncreases.
- BDecreases.
- CRemains constant.
- ✓Is nonuniform.
Answer: D.
View full solution →A solid sphere and a hollow sphere of the same material and of equal radii are heated to the same temperature:
- ABoth will emit equal amount of radiation per unit time in the biginning.
- BBoth will absorb equal amount of radiation from the surrounding in the biginning.
- CThe initial rate of cooling $\Big(\frac{\text{dT}}{\text{dt}}\Big)$ will be the same for the two spheres.
- ✓Both $A$ and $B$
Answer: D.
View full solution →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?
The temperature of the atmosphere at a high altitude is around 500°C. Yet an animal there would freeze to death and not boil. Explain.
Assume that the total surface area of a human body is $1.6 \mathrm{~m}^2$ and that it radiates like an ideal radiator. Calculate the amount of energy radiated per second by the body if the body temperature is $37^{\circ} \mathrm{C}$. Stefan constant $\sigma$ is $6.0 \times 10^{-}$ ${ }^8 \mathrm{Wm}^{-2} \mathrm{~K}^{-4}$.
View full solution →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.
An ordinary electric fan does not cool the air, still it gives comfort in summer. Explain.
On a hot summer day we want to cool our room by opening the refrigerator door and closing all the windows and doors. Will the process work ?
Why is a white dress more comfortable than a dark dress in summer?
Calculate the amount of heat radiated per second by a body of surface area $12cm^2$ kept in thermal equilibrium in a room at temperature $20^\circ C$. The emissivity of the surface = 0.80 and $\sigma=6.0\times10^{-8}\text{Wm}^{-2}\text{K}^{-4}.$
View full solution →Water is boiled in a container having a bottom of surface area $25cm^2$, thickness $1.0mm$ and thermal conductivity $50\text{wm}^{-1}{^{\circ}}\text{C}^{-1}.$ 100g of water is converted into steam per minute in the steady state after the boiling starts. Assuming that no heat is lost to the atmosphere, calculate the temperature of the lower surface of the bottom. Latent heat of vaporization of water $=0.26\times10^6\text{Jkg}^{-1}.$
View full solution →The heat current is written as $\frac{\triangle\text{Q}}{\triangle\text{t}}.$ Why don't we write $\frac{\text{dQ}}{\text{dt}}?$
View full solution →The ends of a metre stick a.re maintained at $100^{\circ} \mathrm{C}$ and $0^{\circ} \mathrm{C}$. One end of a rod is maintained at $25^{\circ} \mathrm{C}$. Where should its other end be touched on the metre stick so that there is no heat current in the rod in steady state?
View full solution →A cylindrical rod of length 50cm and cross sectional area $1cm^2$ is fitted between a large ice chamber at 0°C and an evacuated chamber maintained at 27°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°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.
View full solution →A cubical box of volume $216cm^3$ is made up of 0.1cm thick wood. The inside is heated electrically by a 100W heater. It is found that the temperature difference between the inside and the outside surface is 5°C in steady state. Assuming that the entire electrical energy spent appears as heat, find the thermal conductivity of the material of the box.
View full solution →A spherical tungsten piece of radius $1.0cm$ is suspended in an evacuated chamber maintained at $300K$. The piece is maintained at $1000K$ by heating it electrically. Find the rate at which the electrical energy must be supplied. The emissivity of tungsten is $0.30$ and the Stefan constant $\sigma$ is $6.0 \times 10^{-8}Wm^{-2}K^{-4}$.
View full solution →A calorimeter contains $50 g$ of water at $50^{\circ} \mathrm{C}$. The temperature falls to $45^{\circ} \mathrm{C}$ in 10 minutes. When the calorimeter contains $100 g$ of water -at $50^{\circ} 0$, it takes $18$ minutes for the temperature to become $45^{\circ} \mathrm{C}$. Find the water equivalent of the calorimeter.
View full solution →Seven rods $A, B, C, D, E, F$ and $G$ 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 $K_A = K_c = K_0, K_B = K_D = 2K_0, K_E= 3K_0, K_F = 4K_0$, and $K_G = 5K_0$. The rod E is kept at a constant temperature $T_2$ and the rod G is kept at a constant temperature $T_2(T_2 > T_1)$.
View full solution →- Show that the rod F has a uniform temperature $\text{T}=\frac{(\text{T}_1+2\text{T}_2)}{3}.$
- Find the rate of heat flowing from the source which maintains the temperature $T_2$.
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 $2400cm^2$, 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 $= 3.4\times10^5\text{Jkg}^{-1}.$
View full solution →A steel frame $(\text{K}=45\text{Wm}^{-1}{^{\circ}}\text{C}^{-1})$of total length 60cm and cross sectional area $0.20cm^2$, forms three sides of a square. The free ends are maintained at $20^\circ C$ and $40^\circ C$. Find the rate of heat flow through a cross section of the frame.
View full solution →Suppose the bent part of the frame of the previous problem has a thermal conductivity of $780 \mathrm{Js}^{-1} \mathrm{~m}^{-1°} \mathrm{C}^{-1}$ whereas it is $390 \mathrm{Js}^{-1} \mathrm{~m}^{-1°} \mathrm{C}^{-1}$ 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.
View full solution →Cloudy nights are warmer than the nights with clean sky. Explain.
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°C is 130J.
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.
View full solution →
An amount $n$ (in moles) of a monatomic gas at an initial temperature $T_0$ is enclosed in a cylindrical vessel fitted with a light piston. The surrounding air has a temperature $T_5\left(>T_0\right)$ and the atmospheric pressure is $\mathrm{P}_{\mathrm{a}} \cdot$ Heat may be conducted between the surrounding and the gas through the bottom of the cylinder. The bottom has a surface area A, thickness $x$ and thermal conductivity K. Assuming all changes to be slow, find the distance moved by the piston in time t.
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