Why does heat transfer from one source to another?
819186
In very simple terms, nature does not like imbalance.  Heat is a quantity of energy.  So the hot thing has more energy than the cold thing.  The imbalance is got rid of by the hot thing giving up energy, and the cold thing absorbing it.
159463
Thermal energy is heat that comes in 3 forms: conduction, convection, and radiation.  Conduction is when you are cooking on a stove and the heat passes through the metal in the burner and into the pan.  Convection is when air passes over a warm surface and rises or moves because of the increase in energy and takes the thermal energy with it.  Radiation is how the Sun brings energy to the Earth and other planets.  Thermal energy is measured in Joules (J for short) or British Thermal Units (BTUs).  The transfer of heat is measured in Joules per second, or watts, and BTU/hour.\n\nIts use is almost every aspect of our lives, from your body keeping itself warm to cooking to keeping your house warm to chemical reactions that generate heat.  If you want to study thermal energy, you might major in Mechanical Engineering or Physics in college.  I have a degree in Mechanical Engineering.
833582
Yes, convection is heating a substance by moving a heated substance against it.\n\nThere are 3 types of heating: conduction, convection, and radiation.\n\nConduction is the transfer of heat by contact, convection is the transfer of heat by mixing a heated substance with a cooler substance, and radiation is the transfer of radiant heat from a distance (no physical contact between substances).\n\nHope this helps!
225705
Energy can exist in many forms (chemical, electrical, mechanical, light and heat, etc.) and can be converted from one form to another without being lost (conservation of energy).  When solar energy strikes different surfaces it is either mostly reflected (from pure white or mirrors) or absorbed (pure black) or somewhere in between.  Solar energy consists of photons that enter the material and interact with the electrons of atoms (and molecules) and knock the electrons into higher orbits storing energy.  When the electrons fall back to rest orbits they give up their excess energy as photons.  To understand heat transfer, follow the electrons and photons because the black surfaces that absorbed the photons heats up.  Heat may be stored within a material in its solid, liquid and gaseous states.  Atoms of solids vibrate more when hot and transfer some energy to adjacent cooler atoms within a crystal.  Atoms of liquids bump into each other with more force when hot and transfer some energy to cooler atoms.  Atoms within a gas travel at greater velocities when hot and transfer some energy to any other cooler atom it strikes (like pool balls).  Heat stored in vibrating solids atoms and circulating liquid atoms and flying gaseous atoms can transfer energy from hotter to cooler atoms and in fact a copper vessel filled with half water and half air will reach an equilibrium (identical) temperature as all three states warm or cool by transferring heat energy.  At equilibrium, there will still be atoms well above or below the equilibrium temperature which is only an average temperature.  Thus you can have steam in an ice cube or ice in a flow of steam depending upon the instantaneous (and highly temporary) state or two or more adjacent atoms, but all are driven back toward the equilibrium state by additional collisions or vibrations of neighbors.\n\nThat said, heat is transferred from solid to solid in contact (metal pot on electrical heating element?) by conduction as vibrations of hot neighbors affect cooler neighbors.  Heat is transferred by conduction (from the pot to liquid at the bottom?) by metal atoms vibrating against liquid atoms.  The hot liquid at the bottom of the pot is less dense (due to expansion caused by liquid atom vibrations and electrons in higher orbits) and rises to the top by convection (stirring or forced convection helps).  If you hold your hand near the pot you can feel heat similar to solar heat of radiation.  As electrons in the heated metal fall from higher energetic orbits to rest orbits, photons are transmitted to your hand raising some of your oown electrons to higher (hotter) orbits.\n\nInterestingly, if you open the drapes of your picture window on a frigid winter day, radiation energy will enter your house from outside while even more radiation is leaving from inside, and the net effect will be to cool the house, unless the sun is shining brightly through the window.  It sounds strange but if the interior of your house was at absolute zero temperature the same radiation from the "cold" outside would enter and heat it, right?
957059
A.  They all transfer heat to the air.
180504
Heat is actually a microscale form of kinetic energy. The molecules of a hot object are in rapid motion; the hotter, the higher the average speed. If the object is gaseous the motion consists of free-path travel and collisions with other molecules. If it is liquid the paths between collisions are shorter, and if solid the motion is vibrational with no secular movement. \nIn conduction, heat is transferred by collisions between molecule populations with different average speeds. The transfer continues until both populations have the same average speed. \nIn convection, heat is transferred by mixing fluids of differing temperature. The mixing can be forced or driven by density differences caused by temperature difference. It is not necessary that molecular collisions occur in convection, since mixing alone changes the average molecular speeds.\nIn radiation, the molecular motion is converted to microwave or infrared energy by rigid motion of molecules or flexing of molecular bonds (ref.). Shorter wavelengths (light, UV, X-rays, gamma rays) are produced at higher temperatures where atomic electrons and nuclei may become involved. Radiative energy is not considered heat, but is converted to heat by absorption.
936508
Neither. Let's have a given that 1 fridge is empty and at 40 degrees inside. The other fridge is full and at 40 degrees. The room that these 2 fridges are in is at 70 degrees. The difference in temperature is the cause for heat to flow from hot to cold. The fridges have insulation that has a certain resistance to heat flow. The heat will flow through the walls of the fridges the same, so then Q(heat flow)=A(area)x(T1(70 degrees)-T2(40 degrees))/R(resistance). The area of heat loss for both fridges are equal,the resistance of both fridges are equal, the temperature differential for both is equal,  so the amount of electricity needed to keep the fridges at 40 degrees is equal.
329300
It doesn't. When work is done a small amount of the system's energy is converted to entropy (heat) and is lost to the system (usually through friction).
108832
There are three ways that thermal energy can be transmitted. (1) By radiation of photons. The photons are absorbed by materials and transfer their kinetic energy to the materials. (2) By convection in liquids and gases. The molecules of the fluid have kinetic energy depending upon their temperature. This energy of motion is transferred  to adjacent molecules.  Also as fluids heat up their density decreases and they rise against gravity in a motion called convection.  (3) By conduction in materials.  As the molecules of the material heat up, their kinetic energy of motion is transferred to adjacent molecules by collision.
918513
Heat transfer in the Earth's atmosphere is dominated by radiation effects, rather than thermal conduction or convection.\n\nIt's complicated, but on average the Earth's surface is a few tens of degrees warmer than the surface of the Moon, which receives the same amount of sunlight, and of course has no atmosphere.
1101939
A thermocuple might be the one you seek. \n\nThe seebeck effect on thermocouple uses this theory, as there are two different material soldered together to make a single V or U shaped bar, there is a point where those two metals met. When we heat that point, the heat will move the electron, and since one metal has different coefficient than the other, so the electron will move from one metal to the other, thus an electric current will be created.\n\nPeltier effect, uses the vice versa theory, thus if we put electrical current through that thermocouple, then the thermocouple will need to absorb heat from it surroundings, thus, it will lower the ambient temperature.\n\nI haven't got any clue on how effective does this "refrigerant" work, but I think It might, might, might, work..
71035
Not 100% sure. But I think its because the air inside isn't moving. The air inside is stationary, while it is continuously circulating outside, which causes changes in the temperature. IMHO
545704
Well, get out your heat transfer text book and start calculating. You should have all the info you should need.
575202
heat is a form of energy.
783904
for radiation - how about someone sitting under the sun? Radiant energy is what heats you from the sun.\n\nFor convection (you seem to change your mind if you want convection or conduction info) you could think in terms of how a convector heater works - the warm air circulating the heat around the room. Convection also applies to liquids too - think of the water in the kettle and the water currents inside making all of the water heat more-or less together.\n\nFor conduction, how about a saucepan sitting on top of a cookers' hotplate?\n\nHeating by radiation is through infrared heat - from the sun, from a light bulb - even a bonfire but that can also be from convection too. Think in terms of "heatwaves" with radiation perhaps.\n\nConduction of heat is when two surfaces of dissimilar temperature are brough together. Some of the heat will travel by conduction (touching) to the cooler object.
390030
heat mainly - the energy is wasted in the form of heat instead of transferable energy
802722
It is thermodynamic concepts. Where the high temperature resorvior heat energy transfer to low temperature resorvior (cool), that process known as absorbtion. It can be both way either heat or cool absorbing system.