Hi there,
I have two questions and I was wondering if anyone would be able to answer them for me!
The first would be: Where does the magnetic energy in magnets come from? It doesn't seem as obvious as the energy say, fire would contain.
and the second is: How does a solar cell convert rays of light into electrical energy?
Thanks in advance!
[PS: No, these aren't questions from a test or an assignment for school.]
1. Magnets don't have energy. They radiate a magnetic field. Moving stuff through that field can induce an energy flow.
2. Photons knock electrons loose from the semiconductor material inside the solar cell.
In either of these cases the energy comes from making electrons move. All this would be covered in any primary 8th grade physics class or textbook. You could have typed your questions into google in a simple form i.e.. "how do magnets make electricity" and "how do solar cells work" and found thousands of good explanations.
2. Photons knock electrons loose from the semiconductor material inside the solar cell.
In either of these cases the energy comes from making electrons move. All this would be covered in any primary 8th grade physics class or textbook. You could have typed your questions into google in a simple form i.e.. "how do magnets make electricity" and "how do solar cells work" and found thousands of good explanations.
QUOTE (WasabiLime+Nov 3 2009, 08:41 AM)
Hi there,
I have two questions and I was wondering if anyone would be able to answer them for me!
The first would be: Where does the magnetic energy in magnets come from? It doesn't seem as obvious as the energy say, fire would contain.
and the second is: How does a solar cell convert rays of light into electrical energy?
Thanks in advance!
[PS: No, these aren't questions from a test or an assignment for school.]
Some people say that everything, including magnets, come from God . . . but that answer is farther from shedding light on your question than it is to propagating theism. It's just a little joke for the people on the forum who have witnessed the excessive pro/con theism battles.
Anyway, I had the idea that magnets become magnetic due to the alignment of molecules according to their polarity. Since someone (I believe RPenner, but can't remember for sure) told me that magnetic force is different from electrostatic force, I guess it is not the alignment of molecular electrostatic polarity into a macro magnetic field that causes magnetism. Still, I thought it was something like this.
I'm not sure if the process of molecular alignment that causes a magnet to magnetize is related to the formation of crystals, which I believe also involves molecular alignment into geometric regularities. Maybe someone brighter than me can provide some insight into whether these two processes are related and how; or whether I am totally off about both and misleading people with speculative knowledge (which I hope I am not - hence the warning).
I have two questions and I was wondering if anyone would be able to answer them for me!
The first would be: Where does the magnetic energy in magnets come from? It doesn't seem as obvious as the energy say, fire would contain.
and the second is: How does a solar cell convert rays of light into electrical energy?
Thanks in advance!
[PS: No, these aren't questions from a test or an assignment for school.]
Some people say that everything, including magnets, come from God . . . but that answer is farther from shedding light on your question than it is to propagating theism. It's just a little joke for the people on the forum who have witnessed the excessive pro/con theism battles.
Anyway, I had the idea that magnets become magnetic due to the alignment of molecules according to their polarity. Since someone (I believe RPenner, but can't remember for sure) told me that magnetic force is different from electrostatic force, I guess it is not the alignment of molecular electrostatic polarity into a macro magnetic field that causes magnetism. Still, I thought it was something like this.
I'm not sure if the process of molecular alignment that causes a magnet to magnetize is related to the formation of crystals, which I believe also involves molecular alignment into geometric regularities. Maybe someone brighter than me can provide some insight into whether these two processes are related and how; or whether I am totally off about both and misleading people with speculative knowledge (which I hope I am not - hence the warning).
Welcome in this so diverse forum...
Magnetic fields contain energy, yes. In magnets, the field is created by electrons.
Any single electron has a minimum magnetic moment which isn't zero. In many materials, electrons are grouped in pairs which cancel out this unit moment, but not in some materials where electrons aren't paired, for instance in some transition elements.
Also, some electron orbitals have a magnetic moment. The ones of lowest energy (1s, 2s) are symmetric but if these are full, next electrons must use other orbitals which, in their very nature, have both a kinetic moment and a magnetic moment. Then, it's again a matter of electron pairing or not.
So in both cases (intrinsic moment and orbital moment) the electron has no state available where it would have no magnetic moment.
Now, as pairing electrons is energetically very efficient, you imagine that magnetic materials are an exception.
In addition, it needs some process that lets individual moments add up instead of each orienting itself randomly.
By the way, magnetism is a property of molecules, not atoms. Some alloys composed mainly of Fe-Ni are not magnetic, but CrO2, or some Mn-Zn alloys, are.
-----
In a solar cell, electrons stay in the semiconductor of course. When a suitable photon is absorbed, it dislodges an electron from one place (creating a "hole" - a place where an electron is missing) and makes it mobile. Then, the solar cell is designed to separate the mobile electron from the hole and allow them to reunite only through the external circuitry, which can thus use the produced power.
Magnetic fields contain energy, yes. In magnets, the field is created by electrons.
Any single electron has a minimum magnetic moment which isn't zero. In many materials, electrons are grouped in pairs which cancel out this unit moment, but not in some materials where electrons aren't paired, for instance in some transition elements.
Also, some electron orbitals have a magnetic moment. The ones of lowest energy (1s, 2s) are symmetric but if these are full, next electrons must use other orbitals which, in their very nature, have both a kinetic moment and a magnetic moment. Then, it's again a matter of electron pairing or not.
So in both cases (intrinsic moment and orbital moment) the electron has no state available where it would have no magnetic moment.
Now, as pairing electrons is energetically very efficient, you imagine that magnetic materials are an exception.
In addition, it needs some process that lets individual moments add up instead of each orienting itself randomly.
By the way, magnetism is a property of molecules, not atoms. Some alloys composed mainly of Fe-Ni are not magnetic, but CrO2, or some Mn-Zn alloys, are.
-----
In a solar cell, electrons stay in the semiconductor of course. When a suitable photon is absorbed, it dislodges an electron from one place (creating a "hole" - a place where an electron is missing) and makes it mobile. Then, the solar cell is designed to separate the mobile electron from the hole and allow them to reunite only through the external circuitry, which can thus use the produced power.
QUOTE
All this would be covered in any primary 8th grade physics class or textbook. You could have typed your questions into google in a simple form
He probably did and got these forums as those subjects have been discussed and would result in showing up in a google search. Although bravo in stating it in such an insulting manner, assuming the person is well beyond 8th grade in both academics and maturity.
To the OP:
Your best bet would be to look it up on wiki. I never have for magnetism but I've read up on solar cells and they do a very good job at explaining it.
Wow, some you of guys are rough. Granted the answers to his question could be easily found by doing a little googling, but maybe he did try that and just doesn't understand those explanations. I say let's just help him out. Its not like his questions are completely simple for most people; as some of the questions I've seen posted are just simply stupid and not even worth answering.
First the energy stored within a magnetic field is a potential energy source. That is until it is set in motion some how, it simply has the capability of doing work on an object. An iron bar magnet for example gets its magnetic field from the spinning of the electrons within the element (iron is an element, its number 26 on the periodic table). That is, the majority of the electrons within the iron bar are spinning in the same direction. Moving charge creates a magnetic field. Typically most substances have their electrons spinning in direction such that about half spin one way while the other half spin the other way; hence any magnetic field induced is canceled out inside of itself and is non-magnetic. Furthermore most substances if they come into contact with a magnetic field won't change the direction of the spin of their electrons; iron is not one of these materials. It is very permeable and its electrons can be made to spin in the same direction very easily.
So its the fact that the majority of the electrons inside the iron bar spin in the same direction that causes a magnetic field to emanate from that substance. And yes, both electric and magnetic fields have a potential to due work, a potential energy. To say a magnetic field has no energy is incorrect.
As far as a solar cell. What you need is something called a semiconducting material in order to convert incoming EM waves (or photons if you will) in the visible spectrum into electrical energy that can be used to do work. A semiconductor is composed of a N-type material and a P-type material. The N-type material has more free electrons than the P-type material which is actually lacking in a number of electrons. That's not to say that there exists a charge within the material, its just how its "doped" such that one type is more capable of giving up an electron while the other is more capable of taking on an electron.
When a photon strikes the semiconducting material it typically exerts its incoming energy onto a free electron within the N-type material which causes that electron to "jump" over the junction between the different types of material, which in turns pushes one electron off the same side it jumped over to. The lack of electrons within the P-type material is often called holes. That is, little positive places that an electron can jump into and when paired become neutral. In reality there is no such real thing called a hole, it just used to represent the electrons that are not there. So the photon strikes the electron within the N-type material exciting to the point where it can jump the junction between the materials and lands in a "hole" on the P-type materials side. This addition of an electron to the P-type side is unwanted by the P-type material so it takes one of its free electrons and shoves it out of itself. If a conductive wire is connected to each material type what you find is that as more photons strike the semiconductor a greater amount of electrons are pushed off the P-type side and travel around back to the N-type side through the conductive wire. Not immediately though, as one electron after another is pushed off the P-type side is simply pushes on free electrons within the wire such the the next electron closest to the N-type side is pushed onto/into the N-type side.
So its not the same electron that is pushed off the P side that ends up being pushed onto the N side, its the next one "in line" that is pushed into the N type side from the repulsive force of the electron that was pushed into the wire from the P type side.
I hope that helps. I wouldn't be bothered by other statements telling you an 8th grade physics textbook would answer your questions. My nephew is in the eighth grade and there are no physic courses taught to eighth graders. Physics starts in the 9th grade and even then while they would probably cover magnetism, I don't think you would find anything on the photoelectric effect in a 9th grade physics textbook; maybe, but that's not the point. I feel your questions are legitimate questions. Furthermore to the "smart" guy first you're incorrect about magnetic fields as they do poses a potential energy and furthermore moving electrons do not create energy, it takes an energy source just to keep them in motion. They impart some of their kinetic energy into a magnetic field surrounding their direction of travel, but they don't create energy. They store some of it within their surrounding magnetic field and are constantly dissipating energy while they travel (unless they are guided by a superconductor). Get your facts right before you criticize someone else.
First the energy stored within a magnetic field is a potential energy source. That is until it is set in motion some how, it simply has the capability of doing work on an object. An iron bar magnet for example gets its magnetic field from the spinning of the electrons within the element (iron is an element, its number 26 on the periodic table). That is, the majority of the electrons within the iron bar are spinning in the same direction. Moving charge creates a magnetic field. Typically most substances have their electrons spinning in direction such that about half spin one way while the other half spin the other way; hence any magnetic field induced is canceled out inside of itself and is non-magnetic. Furthermore most substances if they come into contact with a magnetic field won't change the direction of the spin of their electrons; iron is not one of these materials. It is very permeable and its electrons can be made to spin in the same direction very easily.
So its the fact that the majority of the electrons inside the iron bar spin in the same direction that causes a magnetic field to emanate from that substance. And yes, both electric and magnetic fields have a potential to due work, a potential energy. To say a magnetic field has no energy is incorrect.
As far as a solar cell. What you need is something called a semiconducting material in order to convert incoming EM waves (or photons if you will) in the visible spectrum into electrical energy that can be used to do work. A semiconductor is composed of a N-type material and a P-type material. The N-type material has more free electrons than the P-type material which is actually lacking in a number of electrons. That's not to say that there exists a charge within the material, its just how its "doped" such that one type is more capable of giving up an electron while the other is more capable of taking on an electron.
When a photon strikes the semiconducting material it typically exerts its incoming energy onto a free electron within the N-type material which causes that electron to "jump" over the junction between the different types of material, which in turns pushes one electron off the same side it jumped over to. The lack of electrons within the P-type material is often called holes. That is, little positive places that an electron can jump into and when paired become neutral. In reality there is no such real thing called a hole, it just used to represent the electrons that are not there. So the photon strikes the electron within the N-type material exciting to the point where it can jump the junction between the materials and lands in a "hole" on the P-type materials side. This addition of an electron to the P-type side is unwanted by the P-type material so it takes one of its free electrons and shoves it out of itself. If a conductive wire is connected to each material type what you find is that as more photons strike the semiconductor a greater amount of electrons are pushed off the P-type side and travel around back to the N-type side through the conductive wire. Not immediately though, as one electron after another is pushed off the P-type side is simply pushes on free electrons within the wire such the the next electron closest to the N-type side is pushed onto/into the N-type side.
So its not the same electron that is pushed off the P side that ends up being pushed onto the N side, its the next one "in line" that is pushed into the N type side from the repulsive force of the electron that was pushed into the wire from the P type side.
I hope that helps. I wouldn't be bothered by other statements telling you an 8th grade physics textbook would answer your questions. My nephew is in the eighth grade and there are no physic courses taught to eighth graders. Physics starts in the 9th grade and even then while they would probably cover magnetism, I don't think you would find anything on the photoelectric effect in a 9th grade physics textbook; maybe, but that's not the point. I feel your questions are legitimate questions. Furthermore to the "smart" guy first you're incorrect about magnetic fields as they do poses a potential energy and furthermore moving electrons do not create energy, it takes an energy source just to keep them in motion. They impart some of their kinetic energy into a magnetic field surrounding their direction of travel, but they don't create energy. They store some of it within their surrounding magnetic field and are constantly dissipating energy while they travel (unless they are guided by a superconductor). Get your facts right before you criticize someone else.
QUOTE (H2O+Nov 6 2009, 06:48 PM)
He probably did and got these forums as those subjects have been discussed and would result in showing up in a google search. Although bravo in stating it in such an insulting manner, assuming the person is well beyond 8th grade in both academics and maturity.
To the OP:
Your best bet would be to look it up on wiki. I never have for magnetism but I've read up on solar cells and they do a very good job at explaining it.
Thank you. [Also, I am a she
]And you're right, I am very much so past eighth grade. We also didn't cover those questions in my eighth grade science class. Our curriculum is slightly different than that of America's [and anywhere else for that matter.] Here, we don't have physics as a science course for elementary or junior high students. Only in high school. In high school we covered it very briefly in tenth grade.
So thanks for all of the responses, and thank you to Craig for going into extreme detail with your explanation!
My pleasure.
If someone is going to criticize your questions as being too simple they should know the answers to them at the very least. Never mind the fact that it is simply rude. I take it you're not from the USA. I can ensure you that there are many good people in this country, but like everywhere, there are others who have problems; as you can tell from one or two of the replies.
Many Smiles,
Craig
If someone is going to criticize your questions as being too simple they should know the answers to them at the very least. Never mind the fact that it is simply rude. I take it you're not from the USA. I can ensure you that there are many good people in this country, but like everywhere, there are others who have problems; as you can tell from one or two of the replies.
Many Smiles,
Craig
The explanation about solar cells is almost right...
Except that the absorbed photon takes a (valence) electron from a zone (called "depleted") that is nearly void of (conduction) electrons nor holes, and this "created" electron (or rather, pulled from valence to conduction) is sucked by the N-side of the junction, while the created hole is sucked by the P-type side.
By the way, solar cells could more varied than just PN junctions. One could use Shottky junctions, heterojunctions... And some metal/void cells do exist.
So often a good introduction:
http://en.wikipedia.org/wiki/Solar_cell
Except that the absorbed photon takes a (valence) electron from a zone (called "depleted") that is nearly void of (conduction) electrons nor holes, and this "created" electron (or rather, pulled from valence to conduction) is sucked by the N-side of the junction, while the created hole is sucked by the P-type side.
By the way, solar cells could more varied than just PN junctions. One could use Shottky junctions, heterojunctions... And some metal/void cells do exist.
So often a good introduction:
http://en.wikipedia.org/wiki/Solar_cell
QUOTE (Craig+Nov 16 2009, 12:04 AM)
If someone is going to criticize your questions as being too simple they should know the answers to them at the very least.
How's things up on that horse's back? Pretty high eh?
LOL.
My answers were correct. And I have a reasonably full understanding of the subject or I wouldn't have bothered to answer. Your answer was exponential overkill and only confused the poor questioner. Mine encouraged her to start with the basics. It's wasn't an insult. It was a clear and simple statement.
How's things up on that horse's back? Pretty high eh?
LOL.
My answers were correct. And I have a reasonably full understanding of the subject or I wouldn't have bothered to answer. Your answer was exponential overkill and only confused the poor questioner. Mine encouraged her to start with the basics. It's wasn't an insult. It was a clear and simple statement.
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