To transfer heat from one point to another, the mode of transfer which does not ...
Question
To transfer heat from one point to another, the mode of transfer which does not need any medium is
Options
Related Lesson: Heat Transfer Methods | Heat and Heat Transfer Methods
The correct answer is A.
Explanation:
Generally speaking heat flows from a region of high temperature to a region of low temperature. The process whereby heat moves from point to another is known as heat transfer.
Heat transfer processes are three in number: conduction, conviction and radiation.
Conduction: Is a heat transfer process by which heat energy is transferred through a material such that the average position of the particles of the material remain the same. If we consider a slab of face area and thickness L, whose faces are maintained at temperatures. TH and TC by a hot reservoir and a cold reservoir. The rate of heat transfer (Q/t) from its hot surface to its cold surface is given by Q/t = KA((TH - TC)/L) where K is called thermal conductivity, which is simply defined as the ability of a metal to conduct heat. It is measure in W/mk.
Convection: Is the process by which heat is transferred in a liquid or gas by the actual movement of the heated fluid from the hotter to the colder parts.
For a fluid flowing over a solid surface, the rate of heat flow by conviction Q, from the surface to the fluid (or vice-versa) is given by:
Q = hA (Ts × Tf)
Where
h = Conventional heat transfer co-efficient
A = Area of between the surface and the fluid
Tf = Temperature of the main body of the fluid
Ts = Temperature of the surface
Radiation: Is the process by which heat is transferred from a hotter to a cooler body without heating of the intervening medium. The rate Prad at which an object emits energy via electromagnetic radiation depends on the object's surface area and the temperature T of that area in Kelvins and is given by Prad = σEAT4
Where σ = Stefan-Boltzmann constant, and E = emissivity for a black body, E=1
NB: The double-walled glass of a vacuum flask prevent heat loss by conduction or convention
The inside of a vacuum flask is silver line to prevent heat loss by radiation
The cork stopper or cork support prevent heat loss by conduction.
Calorimeter is used so as to prevent heat loss by conduction and radiation
Calorimeter is provided with lid so as to prevent heat loss by convention and evaporation
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Generally speaking heat flows from a region of high temperature to a region of low temperature. The process whereby heat moves from point to another is known as heat transfer.
Heat transfer processes are three in number: conduction, conviction and radiation.
Conduction: Is a heat transfer process by which heat energy is transferred through a material such that the average position of the particles of the material remain the same. If we consider a slab of face area and thickness L, whose faces are maintained at temperatures. TH and TC by a hot reservoir and a cold reservoir. The rate of heat transfer (Q/t) from its hot surface to its cold surface is given by Q/t = KA((TH - TC)/L) where K is called thermal conductivity, which is simply defined as the ability of a metal to conduct heat. It is measure in W/mk.
Convection: Is the process by which heat is transferred in a liquid or gas by the actual movement of the heated fluid from the hotter to the colder parts.
For a fluid flowing over a solid surface, the rate of heat flow by conviction Q, from the surface to the fluid (or vice-versa) is given by:
Q = hA (Ts × Tf)
Where
h = Conventional heat transfer co-efficient
A = Area of between the surface and the fluid
Tf = Temperature of the main body of the fluid
Ts = Temperature of the surface
Radiation: Is the process by which heat is transferred from a hotter to a cooler body without heating of the intervening medium. The rate Prad at which an object emits energy via electromagnetic radiation depends on the object's surface area and the temperature T of that area in Kelvins and is given by Prad = σEAT4
Where σ = Stefan-Boltzmann constant, and E = emissivity for a black body, E=1
NB: The double-walled glass of a vacuum flask prevent heat loss by conduction or convention
The inside of a vacuum flask is silver line to prevent heat loss by radiation
The cork stopper or cork support prevent heat loss by conduction.
Calorimeter is used so as to prevent heat loss by conduction and radiation
Calorimeter is provided with lid so as to prevent heat loss by convention and evaporation