The first is the temperature gradient which is the description of the direction in which the heat is flowing and the rate of transfer. The process of conduction from a hot source to a cold source or a source lacking in heat energy continues until both bodies reach a state of thermal equilibrium. Another important factor is the size of the objects involved. Larger objects require more heat to be warmed up but at the same time, they lose heat faster.
This is because the bigger their surface area is, the more they come into contact with the open air. The physical properties of the objects must also be taken into account. This is because wood is a bad conductor. However, if you were to use a metal spoon heat will be transferred to it very quickly because the metal is a good conductor.
Poor conductors are also called insulators. They prevent energy from flowing away from the source. For example, polar bears are able to survive in arctic regions because their fur serves as an insulator that traps heat inside the body. When the mass motion of a fluid due to the heated fluid moving away from the source heat occurs, it carries energy with it.
This is also a form of heat transfer and it is called convection. This process happens because heat decreases the density of fluids like air and water. The loss of density causes the fluid to rise thereby creating convection currents that can transfer energy.
As the heated layers of the fluid rise, the colder layers which still retain their density descend towards the heat source until they become heated and begin to rise. There are two kinds of convection — spontaneous and forced.
In the former, convection occurs naturally due to buoyancy. The difference in temperature causes a difference in densities. Cause Due to temperature difference. Due to density difference. Occurs from all objects, at temperature greater than 0 K. Occurence Occurs in solids, through molecular collisions. Occurs in fluids, by actual flow of matter. Occurs at a distance and does not heats the intervening substance.
Transfer of heat Uses heated solid substance. Uses intermediate substance. Uses electromagnetic waves. Conduction can be understood as the process, which enables direct transfer of heat through the matter, due to the difference in temperature, between adjacent parts of the object. It happens when the temperature of the molecules present in a substance increase, resulting in vigorous vibration.
The molecules collide with surrounding molecules, making them vibrate too, resulting in the transportation of thermal energy to neighbouring part of the object. In simple terms, whenever two objects are in direct contact with one another, there will be a transfer of heat from the hotter object to the colder one, which is due to conduction.
Further, the objects which permit heat to travel easily through them are called conductors. In science, Convection implies the form of heat transfer, by real movement of matter, that occurs only in fluids. Fluid alludes to any substance, whose molecules move freely from one place to another, such as liquid and gases.
It happens naturally or even forcefully. Gravity has a great role to play in natural convection such that when the substance is heated from below, leads to the expansion of the hotter part. Due to buoyancy, the hotter substance rises as it is less dense and the colder substance replaces it by sinking at the bottom, due to high density, which when gets hot moves upward, and the process continues. When the convection is performed forcefully, the substance is compelled to move upwards by any physical means such as the pump.
Air heating system. The heat transfer mechanism in which no medium is required is called radiation. It refers to the movement of heat in waves, as it does not need molecules to travel through. The object need not be in direct contact with one another to transmit heat. Whenever you feel heat without actually touching the object, it is because of radiation.
Moreover, colour, surface orientation, etc. In this process, the energy is transmitted through electromagnetic waves called as radiant energy. Hot objects generally emit thermal energy to cooler surroundings. Radiant energy is capable of travelling in the vacuum from its source to the cooler surroundings. These waves are of the same nature as sound but have very much higher frequencies and their energies are quantized as phonons.
On balance, more energy is transferred by phonons from hotter to colder parts of than is transferred the opposite way. Theories of heat conduction treat the phonons as if they were gas molecules moving within the space occupied by the solid, being scattered by irregularities in the material.
Conduction in nonmetallic liquids is intermediate in character between that in solids and that in gasses. See also: Thermal conductivity. The process of transfer of heat in a fluid by the movement of the fluid itself. There are two types of convection of heat:.
See Also: Convection current. Radiation is one of the ways of modes of heat transfer in which heat is transferred directly in the form of waves. The heat reached on the earth from The Sun is an example of radiation heat transfer.
See also: Blackbody radiation. Watch the video to learn about the difference between heat transfer methods by conduction , convection , and radiation. Related topics. Your email address will not be published.
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