cam875
Oct1-08, 05:36 PM
can somebody tell me all the easiest ways to generate heat, it doesnt have to be a lot but some. thanks in advance.
View Full Version : thermodynamics
Hootenanny
Oct1-08, 06:33 PM
can somebody tell me all the easiest ways to generate heat, it doesnt have to be a lot but some. thanks in advance.
When you say ''generate heat', do you mean a process that transfers thermal energy to the environment?[/
When you say ''generate heat', do you mean a process that transfers thermal energy to the environment?[/
cam875
Oct1-08, 06:39 PM
if I wanted to energize a particle or atom by applying heat to it what is the best way to do that to the particle/atom.
Hootenanny
Oct1-08, 06:52 PM
if I wanted to energize a particle or atom by applying heat to it what is the best way to do that to the particle/atom.
Although it would be practically difficult to do with an individual atom, the best method for a fluid would be to run a high current through a long coil of wire made from a material with a high resistivity. This is the same principle through which electrical heaters and incandescent light bulbs work.
Although it would be practically difficult to do with an individual atom, the best method for a fluid would be to run a high current through a long coil of wire made from a material with a high resistivity. This is the same principle through which electrical heaters and incandescent light bulbs work.
DeShark
Oct2-08, 06:16 AM
Although it would be practically difficult to do with an individual atom, the best method for a fluid would be to run a high current through a long coil of wire made from a material with a high resistivity. This is the same principle through which electrical heaters and incandescent light bulbs work.
Why not excite the molecules directly rather than heating up a metal object and then transfering this energy to the water. i.e. use a microwave?
It depends on what you're heating though I guess. What are you trying to heat?
Generating heat can be done through numerous processes: chemical, frictional, etc... which one is best depends on the specifics.
In these specifics, i.e. individual atoms/particles, I'd say shoot a photon at it, with the right frequency.
Edit: P.S. heat is more of a macroscopic entity. Energy = heat essentially. So you want to increase the (kinetic) energy of the atom/particle. The increased energies of individual particles in a solid/gas/whatever is what we observe as an increase in temperature.
Why not excite the molecules directly rather than heating up a metal object and then transfering this energy to the water. i.e. use a microwave?
It depends on what you're heating though I guess. What are you trying to heat?
Generating heat can be done through numerous processes: chemical, frictional, etc... which one is best depends on the specifics.
In these specifics, i.e. individual atoms/particles, I'd say shoot a photon at it, with the right frequency.
Edit: P.S. heat is more of a macroscopic entity. Energy = heat essentially. So you want to increase the (kinetic) energy of the atom/particle. The increased energies of individual particles in a solid/gas/whatever is what we observe as an increase in temperature.
Hootenanny
Oct2-08, 06:20 AM
Why not excite the molecules directly rather than heating up a metal object and then transfering this energy to the water. i.e. use a microwave?
I suggested using a heating element because the OP specifically mentioned the process of heat transfer. Of course photon excitation would be more straight forward, but then that would heat transfer.
Energy = heat essentially
I'm sorry but I really can't let this slide (this is a pet hate of mine), heat is not the same as energy. Heat is more analagous to mechanical work than energy.
I suggested using a heating element because the OP specifically mentioned the process of heat transfer. Of course photon excitation would be more straight forward, but then that would heat transfer.
Energy = heat essentially
I'm sorry but I really can't let this slide (this is a pet hate of mine), heat is not the same as energy. Heat is more analagous to mechanical work than energy.
cam875
Oct2-08, 07:01 AM
well how does the sun produce heat and light, does it have some source of power?
stewartcs
Oct2-08, 09:02 AM
Like Hootenanny has already pointed out, systems contain energy, not heat or work. Heat and work are transport mechanisms for energy across a system boundary.
CS
CS
Type_R
Oct2-08, 12:11 PM
well how does the sun produce heat and light, does it have some source of power?
Energy emitted from Nuclear fusion if i'm not mistaken, and this energy gets emitted in the form of radiation.
Kinda like a L.E.D.....When electrons are going across the depletion layer, they slide down a "energy hill" as they go down to lower energy levels they emit radiation in the form of a photon or light..... in other diodes its emitted in the form of heat.
Energy emitted from Nuclear fusion if i'm not mistaken, and this energy gets emitted in the form of radiation.
Kinda like a L.E.D.....When electrons are going across the depletion layer, they slide down a "energy hill" as they go down to lower energy levels they emit radiation in the form of a photon or light..... in other diodes its emitted in the form of heat.
DeShark
Oct2-08, 04:34 PM
I'm sorry but I really can't let this slide (this is a pet hate of mine), heat is not the same as energy. Heat is more analagous to mechanical work than energy.
No, you're completely right. I was using heat in a similar context as the o.p. A more familiar usage if you will. You're right to correct it. What I should've said is that Thermal Energy = Temperature (with a constant factor of the boltzman constant), according to classical thermodynamics (Using Quantum Mech and Statistical Physics, there's the zero-point energy to contend with, so this isn't true in the low energy limit, I know). But increasing the kinetic energy of individual molecules/atoms increases the temperature and vice versa to increase the temperature (transfer heat to) is the same thing as increasing its energy...
But isn't it much easier to be slightly less technically accurate for the above purposes?
No, you're completely right. I was using heat in a similar context as the o.p. A more familiar usage if you will. You're right to correct it. What I should've said is that Thermal Energy = Temperature (with a constant factor of the boltzman constant), according to classical thermodynamics (Using Quantum Mech and Statistical Physics, there's the zero-point energy to contend with, so this isn't true in the low energy limit, I know). But increasing the kinetic energy of individual molecules/atoms increases the temperature and vice versa to increase the temperature (transfer heat to) is the same thing as increasing its energy...
But isn't it much easier to be slightly less technically accurate for the above purposes?
DeShark
Oct2-08, 04:56 PM
well how does the sun produce heat and light, does it have some source of power?
In the centre of the sun, under immense gravitational fields, the hydrogen molecules are moving so fast that (along with a bit of Quantum Tunnelling) they are able to overcome the coulomb interaction which separates them and combine to make Deuteron, a positron, the antiparticle pair of the electron (i.e. one proton decays into a neutron) and a bit of binding energy. A nearby electron annihilates with the positron, producing two photons a la E=mc^2 (lots of energy). Then another photon is able to fuse with the deuteron to form a light isotope of Helium. This releases more energy, because of the energy difference between the proton and the deuteron and the helium isotope. After this, the light helium can fuse either with another light helium atom to produce normal helium plus 2 hydrogen atoms, or it can combine with a normal helium atom to produce beryllium.
Most(all?) of these combinations release energy. In one full chain, we get 26.73 MeV of energy (quite a lot!). This energy appears as both heating of the sun and radiation of energy outwards from the sun (heat and light). I hope this wasn't too involved and/or confusing.
In the centre of the sun, under immense gravitational fields, the hydrogen molecules are moving so fast that (along with a bit of Quantum Tunnelling) they are able to overcome the coulomb interaction which separates them and combine to make Deuteron, a positron, the antiparticle pair of the electron (i.e. one proton decays into a neutron) and a bit of binding energy. A nearby electron annihilates with the positron, producing two photons a la E=mc^2 (lots of energy). Then another photon is able to fuse with the deuteron to form a light isotope of Helium. This releases more energy, because of the energy difference between the proton and the deuteron and the helium isotope. After this, the light helium can fuse either with another light helium atom to produce normal helium plus 2 hydrogen atoms, or it can combine with a normal helium atom to produce beryllium.
Most(all?) of these combinations release energy. In one full chain, we get 26.73 MeV of energy (quite a lot!). This energy appears as both heating of the sun and radiation of energy outwards from the sun (heat and light). I hope this wasn't too involved and/or confusing.
Hootenanny
Oct3-08, 04:48 AM
But isn't it much easier to be slightly less technically accurate for the above purposes?
Whilst I agree that the OP incorrectly used heat as a synonym for internal energy, I cannot agree that we should not be correct in our responses simply because it is easier. The distinction between heat and internal energy is one which becomes increasing blurred, not just in the general population but also is the educational system. Many physics high school (and even undergraduate) students think of heat and internal energy as the same quantity. Whilst there isn't too much of a problem at the elementary level, once one begins to study thermodynamics the distinction between heat and internal energy is an important concept and the reason why we have two different terms.
Would you have let it slide if I'd have said "The easiest way to increase and object's work is to..." or would have said "energy = work"?
Whilst I agree that the OP incorrectly used heat as a synonym for internal energy, I cannot agree that we should not be correct in our responses simply because it is easier. The distinction between heat and internal energy is one which becomes increasing blurred, not just in the general population but also is the educational system. Many physics high school (and even undergraduate) students think of heat and internal energy as the same quantity. Whilst there isn't too much of a problem at the elementary level, once one begins to study thermodynamics the distinction between heat and internal energy is an important concept and the reason why we have two different terms.
Would you have let it slide if I'd have said "The easiest way to increase and object's work is to..." or would have said "energy = work"?
atyy
Oct3-08, 05:14 AM
"The first law states that both work and heat are forms of energy, and that the total energy is conserved."
Kardar, Lecture 1:
http://ocw.mit.edu/OcwWeb/Physics/8-333Fall-2005/LectureNotes/index.htm
Kardar, Lecture 1:
http://ocw.mit.edu/OcwWeb/Physics/8-333Fall-2005/LectureNotes/index.htm
Hootenanny
Oct3-08, 05:32 AM
"The first law states that both work and heat are forms of energy, and that the total energy is conserved."
Kardar, Lecture 1:
http://ocw.mit.edu/OcwWeb/Physics/8-333Fall-2005/LectureNotes/index.htm
I would have to disagree with that, instead I would say something like "The first law is a statement of the principle of conservation of energy and says that the internal energy of a system is the sum of the heat added to the system and the work done on the system.".
Work and heat are methods of energy transfer rather than forms of energy.
Kardar, Lecture 1:
http://ocw.mit.edu/OcwWeb/Physics/8-333Fall-2005/LectureNotes/index.htm
I would have to disagree with that, instead I would say something like "The first law is a statement of the principle of conservation of energy and says that the internal energy of a system is the sum of the heat added to the system and the work done on the system.".
Work and heat are methods of energy transfer rather than forms of energy.
stewartcs
Oct3-08, 08:27 AM
"The first law states that both work and heat are forms of energy, and that the total energy is conserved."
Kardar, Lecture 1:
http://ocw.mit.edu/OcwWeb/Physics/8-333Fall-2005/LectureNotes/index.htm
This is erroneous. Systems do not contain heat or work, they contain energy. Hence, heat and work are not energy. Heat and work are energy transport mechanisms between a system and its surroundings.
Heat and work are boundary phenomena, as such they are only recognized at the boundaries of a system as they cross the boundaries.
Both are associated with a process, not a state.
Both are path functions. In other words their magnitudes depend on the path followed.
CS
Kardar, Lecture 1:
http://ocw.mit.edu/OcwWeb/Physics/8-333Fall-2005/LectureNotes/index.htm
This is erroneous. Systems do not contain heat or work, they contain energy. Hence, heat and work are not energy. Heat and work are energy transport mechanisms between a system and its surroundings.
Heat and work are boundary phenomena, as such they are only recognized at the boundaries of a system as they cross the boundaries.
Both are associated with a process, not a state.
Both are path functions. In other words their magnitudes depend on the path followed.
CS
cam875
Oct4-08, 05:00 PM
wow some of this just got beyond me lol, but thanks for the informed answers.
cam875
Oct4-08, 09:16 PM
ok I from one of the previous posts in this thread there is a lot of talk about different kinds of atoms being used in the process of radiation and everything that the sun uses. But since matter is never created or destroyed do these atoms leave the sun when there used up and travel through space to earth or other planets and different things or do they stay and keep returning the process, and thus the sun can keep using the same matter over and over again. Because if the matter is used up or leaves the area of the sun wouldnt it eventually run out of a source of materials and basically die.
russ_watters
Oct5-08, 10:41 PM
ok I from one of the previous posts in this thread there is a lot of talk about different kinds of atoms being used in the process of radiation and everything that the sun uses. But since matter is never created or destroyed do these atoms leave the sun when there used up and travel through space to earth or other planets and different things or do they stay and keep returning the process, and thus the sun can keep using the same matter over and over again. Because if the matter is used up or leaves the area of the sun wouldnt it eventually run out of a source of materials and basically die. There are a lot of confused thoughts thrown together there, but the answer to the last question is yes, the sun will eventually run out of fuel and die.
cam875
Oct6-08, 04:49 PM
so where does the matter being used up in the chemical reaction that causes the sun to do what it does go since matter cant be destroyed? or is it converted to energy like e=mc^2 and thats wat gives us light and heat.
Also when do scientists expect our sun to die? and if it does do they have a plan to keep our existence going?
Also when do scientists expect our sun to die? and if it does do they have a plan to keep our existence going?
stewartcs
Oct6-08, 05:06 PM
so where does the matter being used up in the chemical reaction that causes the sun to do what it does go since matter cant be destroyed? or is it converted to energy like e=mc^2 and thats wat gives us light and heat.
Also when do scientists expect our sun to die? and if it does do they have a plan to keep our existence going?
http://en.wikipedia.org/wiki/Sun#Life_cycle
CS
Also when do scientists expect our sun to die? and if it does do they have a plan to keep our existence going?
http://en.wikipedia.org/wiki/Sun#Life_cycle
CS
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