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A solid sphere, a cube and a thin circular plate have the same mass and are made of the same material. All of them are heated to the same temperature. The rate of cooling is:
(1) Maximum for the sphere and minimum for the plate
(2) Maximum for the sphere and minimum for the cube
(3) Maximum for the plate and minimum for the sphere
(4) Same for sphere and plate and minimum for the cube

Last updated date: 20th Jun 2024
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Hint: We know that in general, heat transfer describes the flow of heat (thermal energy) due to temperature differences and the subsequent temperature distribution and changes. The study of transport phenomena concerns the exchange of momentum, energy, and mass in the form of conduction, convection, and radiation. The amount of heat transferred by a substance depends on the speed and number of atoms or molecules in motion, according to Energy Education. The faster the atoms or molecules move, the higher the temperature, and the more atoms or molecules that are in motion, the greater the quantity of heat they transfer.

Complete step by step answer
We can say that heat transfer by thermal radiation is transfer of heat by electromagnetic waves. It is different from conduction and convection as it requires no matter or medium to be present. The radiative energy will pass perfectly through vacuum as well as clear air.
We can say that radiation happens when heat moves as energy waves, called infrared waves, directly from its source to something else. This is how the heat from the Sun gets to Earth. In fact, all hot things radiate heat to cooler things. When the heat waves hit the cooler thing, they make the molecules of the cooler object speed up.
We know that since the material is the same, the density is the same.
Since mass is the same and density is same so all three have the same volume.
For the same volume, the surface area of the plate is the largest and of the sphere is the smallest. Same volume, the surface area of the plate is the largest and of the sphere is the smallest. The rate of loss of heat by radiation is proportional to surface area.

So, the correct answer is option B.

Note: We know that conduction transfers heat by direct molecular collision. An area of greater kinetic energy will transfer thermal energy to an area with lower kinetic energy. Higher-speed particles will collide with slower speed particles. The slower-speed particles will increase in kinetic energy as a result. Conduction is the transfer of thermal energy through direct contact. Convection is the transfer of thermal energy through the movement of a liquid or gas. Radiation is the transfer of thermal energy through thermal emission. Conduction is the process by which heat energy is transmitted through collisions between neighbouring atoms or molecules. Conduction occurs more readily in solids and liquids, where the particles are closer to together, than in gases, where particles are further apart.