Peng; Your problem comes from a misunderstanding of Faraday's law...and not recognizing the GRADIENT IN THE FIELD. In your exper. set-up , you fail to realize that there is a GRADIENT in the B field in each direction from the center of the edge of the large magnet which points toward the opposite poles in space..... Therefore you have a magnetic flux crossing the coil as it spins. This is fully in accord with Faraday Law. Lunar
I have modified the figure 4 to show you that the field lines entering and leaving the coil cancel and the flux in the area of the coil is constantly zero. So, no flux variation exists.
You still missed the whole point Peng, especially about the GRADIENT....even though I put it in BOLD CAPS twice. The flux is NOT zero because we have a ROTATING NON-SYMMETRIC coil and because in the vertical direction (above and below the disk) the B field lines are NOT uniform, a fact you failed to show on your figure 3. The coil is NOT symmetric. Thus (in figure 3) when the coil rotates into the "vertical" position (long sides are vertical), the coil intersects a DIFFERENT density of field lines than when it moves into the horizontal position (with respect to the edge of the magnet). Not only does the NUMBER of field lines vary above or below the edge of the magnet, but the DIRECTION of the field lines vary as you go further above or below (as they curl into the poles). Thus as the coil MOVES from vertical position to horizontal position the number of field lines that it intersects VARIES....IOW, A CHANGE IN FLUX OCCURS as it rotates its position with respect to the number and direction of field lines with each quarter turn. Can you see that now?
The mistake you made in your analysis is that you looked at the field lines "entering and leaving" from ONLY ONE COIL POSITION. This is.a common error. You must look at the CHANGE in flux through the coil AS IT MOVES FROM ONE POSITION TO THE NEXT as it rotates to a DIFFERENT position and intersects a DIFFERENT density (and direction) of field lines. IOW, the combination of B Field gradient AND non-symmetric coil makes the flux change inevitable.
If you want to convince anyone, especially a true physicist like myself, that Faraday Law is violated you must use a SYMMETRIC CIRCULAR COIL, so that upon rotation there is no possibility of flux change. (Notice , I said CIRCULAR coil,, a square coil will not do since it can also show an asymmetry in the intersection of field lines at different positions.) A circular coil is necessary to be unambiguous....If you make a perfect CIRCULAR COIL you will see that no EMF will be induced in the coil upon rotation. Without a circular symmetric coil your conclusion is merely verifying Faraday's Law. Lunar
Please see the new figure 3 where I have put the top half and bottom half of the coil in pink and green to show that while the field intensity is not uniform in these areas, the flux in pink and in green are opposite with the same magnitude and cancel. So, the total flux in the coil is zero.
You are STILL analyzing the field lines while the coil is in ONLY ONE POSITION ...You are STILL not getting it Peng; Why do you continue to MIS-quote me?.... ITS NOT ABOUT the flux balancing out while its in ANY ONE position....Its about how the TOTAL FLUX thru the coil CHANGES when rotated to a DIFFERENT position....THAT is what causes the EMF.....exactly as Faraday predicts. There is a DIFFERENT AMOUNT of field lines cut as the coil rotates from one coil POSITION to a NEW POSITION....thus there is flux CHANGE from ONE COIL POSITION to the OTHER POSITION. Not only are there a different NUMBER of field lines cut AT THE NEW POSITION, but AT THE NEW POSITION the field lines intersect at a DIFFERENT ANGLE with respect to the plane of the coil. Did you understand it THAT time? LETS SAY IT TOGETHER AGAIN...You must analyse the field lines at EACH COIL POSITION (How many times do I have to say it? ) AT EACH POSITION>>>>EACH position....in order to determine the AMOUNT of CHANGE in the field lines cut by the coil from ONE POSITION to the OTHER POSITION. ....DUH? DUUUUUH? DOUBLE DUH?
I don't know if you really are that ignorant of Faradays Law by lack of education or if you are purposely ignoring what I said so you can stay in complete denial in order to save your pet theory....Either way; an HONEST experimenter would make a CIRCULAR symmetric coil and RE-TEST. Its simple to do, and would prove the facts to yourself . If you think the flux is NOT based upon the coil dimensions and its change IN POSITION then go ahead and make a CIRCULAR COIL and prove me wrong.......and if you refuse , then all indications are that you are simply AFRAID to admit that you are WRONG....Even if you can't understand the physics of why the amount of enclosed field lines CHANGES from one position to the other position (with a rectangular coil), a simple null test using a circular coil will prove the point.... and that is probably why you refuse to do it.... NON-OBJECTIVE experimentation is done by THOUSANDS of immature amateurs who refuse to do the most simple tests that would show conclusively their error...Is it any wonder their a' priori conclusions are rejected en mass? Their fear of the facts being revealed elicits the very rejection they fear the most. Do you want to join their ranks?
Again... as I stated before... The mistake you ARE STILL MAKING in your analysis is that you looked at the field lines "entering and leaving" from ONLY ONE COIL POSITION. This is.a common error. You must look at the CHANGE in flux through the coil AS IT MOVES FROM ONE POSITION TO THE NEXT as it rotates to a DIFFERENT position and intersects a DIFFERENT density (and direction) of field lines.
I begun with a round coil and it did not generate voltage. If you think this explains the rectangular case, please ignore the following.
I explained you that the flux in the coil canceled out because you haven't understood my point. When the coil rotates, it makes successively the angle 10° 20° 30° .... with the plane of the magnet. In the position of 10°, the flux in the pink area is phi(10), in the green area is -phi(10), the total flux in the coil is phi_coil(10)=phi(10)-phi(10)=0.
In the position of 20°, the flux in the pink area is phi(20), in the green area is -phi(20), the total flux in the coil is phi_coil(20)=phi(20)-phi(20)=0.
the flux in the pink area is phi(30), in the green area is -phi(30), the total flux in the coil is phi_coil(30)=phi(30)-phi(30)=0.......
We see that the total flux is zero constantly and the variation ratio is d phi_coil / dt =d 0 / dt = 0.
Faraday's law states U = d phi / dt , then U =d phi_coil / dt =d 0 / dt = 0.
I appreciate your videos and replies. Good work, Peng! I can think of several follow-up experiments, such as holding the coil parallel to the north face, center, spinning it - then repeating this experiment with the coil tilted. Do you still have the 3,000 turn coil with the 2 LED lights? --Steven Jones
Thank you Steven Jones. I have already done the tilted coil experiment you suggest. Below is the discussion about it and the link where I have put the article about this experiment "Is the tangential EMF due to a tilt of the coil?" http://pengkuanem.blogspot.com/2014/12/is-tangential-emf-due-to-tilt-of-coil.html or https://www.academia.edu/9826402/Is_the_tangential_EMF_due_to_a_tilt_of_the_coil
Peng; Your problem comes from a misunderstanding of Faraday's law...and not recognizing the GRADIENT IN THE FIELD.
ReplyDeleteIn your exper. set-up , you fail to realize that there is a GRADIENT in the B field in each direction from the center of the edge of the large magnet which points toward the opposite poles in space..... Therefore you have a magnetic flux crossing the coil as it spins. This is fully in accord with Faraday Law.
Lunar
I have modified the figure 4 to show you that the field lines entering and leaving the coil cancel and the flux in the area of the coil is constantly zero. So, no flux variation exists.
DeleteYou still missed the whole point Peng, especially about the GRADIENT....even though I put it in BOLD CAPS twice. The flux is NOT zero because we have a ROTATING NON-SYMMETRIC coil and because in the vertical direction (above and below the disk) the B field lines are NOT uniform, a fact you failed to show on your figure 3. The coil is NOT symmetric. Thus (in figure 3) when the coil rotates into the "vertical" position (long sides are vertical), the coil intersects a DIFFERENT density of field lines than when it moves into the horizontal position (with respect to the edge of the magnet).
DeleteNot only does the NUMBER of field lines vary above or below the edge of the magnet, but the DIRECTION of the field lines vary as you go further above or below (as they curl into the poles). Thus as the coil MOVES from vertical position to horizontal position the number of field lines that it intersects VARIES....IOW, A CHANGE IN FLUX OCCURS as it rotates its position with respect to the number and direction of field lines with each quarter turn. Can you see that now?
The mistake you made in your analysis is that you looked at the field lines "entering and leaving" from ONLY ONE COIL POSITION. This is.a common error. You must look at the CHANGE in flux through the coil AS IT MOVES FROM ONE POSITION TO THE NEXT as it rotates to a DIFFERENT position and intersects a DIFFERENT density (and direction) of field lines.
IOW, the combination of B Field gradient AND non-symmetric coil makes the flux change inevitable.
If you want to convince anyone, especially a true physicist like myself, that Faraday Law is violated you must use a SYMMETRIC CIRCULAR COIL, so that upon rotation there is no possibility of flux change.
(Notice , I said CIRCULAR coil,, a square coil will not do since it can also show an asymmetry in the intersection of field lines at different positions.)
A circular coil is necessary to be unambiguous....If you make a perfect CIRCULAR COIL you will see that no EMF will be induced in the coil upon rotation. Without a circular symmetric coil your conclusion is merely verifying Faraday's Law.
Lunar
Please see the new figure 3 where I have put the top half and bottom half of the coil in pink and green to show that while the field intensity is not uniform in these areas, the flux in pink and in green are opposite with the same magnitude and cancel. So, the total flux in the coil is zero.
DeleteYou are STILL analyzing the field lines while the coil is in ONLY ONE POSITION ...You are STILL not getting it Peng; Why do you continue to MIS-quote me?.... ITS NOT ABOUT the flux balancing out while its in ANY ONE position....Its about how the TOTAL FLUX thru the coil CHANGES when rotated to a DIFFERENT position....THAT is what causes the EMF.....exactly as Faraday predicts. There is a DIFFERENT AMOUNT of field lines cut as the coil rotates from one coil POSITION to a NEW POSITION....thus there is flux CHANGE from ONE COIL POSITION to the OTHER POSITION.
DeleteNot only are there a different NUMBER of field lines cut AT THE NEW POSITION, but AT THE NEW POSITION the field lines intersect at a DIFFERENT ANGLE with respect to the plane of the coil.
Did you understand it THAT time?
LETS SAY IT TOGETHER AGAIN...You must analyse the field lines at EACH COIL POSITION (How many times do I have to say it? ) AT EACH POSITION>>>>EACH position....in order to determine the AMOUNT of CHANGE in the field lines cut by the coil from ONE POSITION to the OTHER POSITION. ....DUH? DUUUUUH? DOUBLE DUH?
I don't know if you really are that ignorant of Faradays Law by lack of education or if you are purposely ignoring what I said so you can stay in complete denial in order to save your pet theory....Either way; an HONEST experimenter would make a CIRCULAR symmetric coil and RE-TEST.
Its simple to do, and would prove the facts to yourself . If you think the flux is NOT based upon the coil dimensions and its change IN POSITION then go ahead and make a CIRCULAR COIL and prove me wrong.......and if you refuse , then all indications are that you are simply AFRAID to admit that you are WRONG....Even if you can't understand the physics of why the amount of enclosed field lines CHANGES from one position to the other position (with a rectangular coil), a simple null test using a circular coil will prove the point.... and that is probably why you refuse to do it....
NON-OBJECTIVE experimentation is done by THOUSANDS of immature amateurs who refuse to do the most simple tests that would show conclusively their error...Is it any wonder their a' priori conclusions are rejected en mass? Their fear of the facts being revealed elicits the very rejection they fear the most.
Do you want to join their ranks?
Again... as I stated before... The mistake you ARE STILL MAKING in your analysis is that you looked at the field lines "entering and leaving" from ONLY ONE COIL POSITION. This is.a common error. You must look at the CHANGE in flux through the coil AS IT MOVES FROM ONE POSITION TO THE NEXT as it rotates to a DIFFERENT position and intersects a DIFFERENT density (and direction) of field lines.
DeleteI begun with a round coil and it did not generate voltage. If you think this explains the rectangular case, please ignore the following.
DeleteI explained you that the flux in the coil canceled out because you haven't understood my point. When the coil rotates, it makes successively the angle 10° 20° 30° .... with the plane of the magnet. In the position of 10°,
the flux in the pink area is phi(10),
in the green area is -phi(10),
the total flux in the coil is phi_coil(10)=phi(10)-phi(10)=0.
In the position of 20°,
the flux in the pink area is phi(20),
in the green area is -phi(20),
the total flux in the coil is phi_coil(20)=phi(20)-phi(20)=0.
the flux in the pink area is phi(30),
in the green area is -phi(30),
the total flux in the coil is phi_coil(30)=phi(30)-phi(30)=0.......
We see that the total flux is zero constantly and the variation ratio is
d phi_coil / dt =d 0 / dt = 0.
Faraday's law states U = d phi / dt , then U =d phi_coil / dt =d 0 / dt = 0.
So, for faraday, there should not be voltage.
I appreciate your videos and replies. Good work, Peng! I can think of several follow-up experiments, such as holding the coil parallel to the north face, center, spinning it - then repeating this experiment with the coil tilted. Do you still have the 3,000 turn coil with the 2 LED lights? --Steven Jones
DeleteThank you Steven Jones. I have already done the tilted coil experiment you suggest. Below is the discussion about it and the link where I have put the article about this experiment
Delete"Is the tangential EMF due to a tilt of the coil?" http://pengkuanem.blogspot.com/2014/12/is-tangential-emf-due-to-tilt-of-coil.html
or
https://www.academia.edu/9826402/Is_the_tangential_EMF_due_to_a_tilt_of_the_coil
https://groups.google.com/d/msg/sci.physics.electromag/OE2fhe2wKbw/oC0fLE84OqkJ
I expect that someone else to redo this experiment to confirm my result.