Post by: Mitko Gorgiev on 25/01/2020 23:47:53
THIS POST AND OTHERS BY THE SAME POSTER APPEAR TO BE EDUCATIONAL IN NATURE, HOWEVER THEY CONTAIN SERIOUS ERRORS AND SHOULD NOT BE TAKEN AS SCIENTIFIC PRINCIPLES.
In almost every textbook on electromagnetism where the Faraday’s law of induction is discussed, there is an example of a usually rectangular wire loop which rotates in a magnetic field (drawing below).
wire loop.JPG (9.01 kB . 245x200 - viewed 10174 times)What type of current is induced in this loop? Direct current, alternating current, or maybe, no current?
Consider the following experiment: from a lacquered copper wire we cut off twenty to thirty pieces of about 10 cm. From them we form a bundle of parallel wires and connect the two ends with one more wire each. The other ends of these two wires are connected to a sensitive analog ammeter. We hold the bundle horizontally and move quickly a strong and broad magnet downwards on its left side. The pointer of the instrument will make a deflection to one side. If we now move the magnet quickly downwards on the right side of the bundle, the instrument will make a deflection to the opposite side. The magnetic flux that we have produced in the wire is now in the opposite direction to the one in the first case, which is why the deflection is in the opposite direction. The motion of the magnet produces current even if we only approach it to the bundle from one side without lowering it below the bundle. In this case the current is somewhat weaker. But if we now move the magnet down to the middle of the bundle, the instrument won’t show any current, because the left and the right halve of the magnet act on opposite sides of the bundle, canceling each other out.
We can do the experiment with only a single wire instead of a bundle, as long as we have a very strong magnet and a very sensitive ammeter.
We can imagine that inside this wire there is a propeller or there are many propellers in a row. When we turn a propeller manually from the left side, then it is turning in one direction and it is blowing on one side (plus), but it is suctioning on the other side (minus). When we turn the propeller from the right side, then it is turning in the contrary direction and the air current is in the opposite direction. But we cannot turn the propeller from above. Exactly the same picture we have with the magnet and the wire.
wire propeller.JPG (10.88 kB . 400x221 - viewed 10117 times)After we have lowered the magnet down and have produced a current in one direction, then we can move it back upward. In that case we produce a current in the contrary direction, just as we will produce an air-current in the contrary direction if we turn the propeller from down up.
In producing the current in the rectangular loop, only the two shorter sides of the loop play a role. These relevant sides are marked with “L” in the drawing above. Their length is of no importance at all; the loop could be also a square.
Let’s look at the drawing below.
cross sections.JPG (20.05 kB . 413x321 - viewed 10190 times)The loop in the drawing rotates counter-clockwise. When the right side of the loop moves up, then it is the same as if the upper and the lower magnet move down and the side is still. The induced current thereby flows away from us.
At the same time the left side of the loop moves down. The induced current in that side flows also away from us. Without knowing the right hand rule, we can conclude that the current in both sides flows in the same direction (this means: either towards or away from us) in the following way:
If the right side is moving up, then the current is flowing in one of the two possible directions; if the same side is moving down, then the current is flowing in the contrary direction (please recall on the experiment with the bundle). The reverse applies for the left side of the loop. So, when one side of the loop is moving up and the opposite side, of course, down, then the current in both sides is either towards us or away from us. But since it is a loop, these two currents cancel each other out. We have here something similar to the circuit below, where two identical batteries are connected as shown:
batteries.JPG (4.24 kB . 200x150 - viewed 10056 times)No current can flow through this circuit.
The induced current in one of the relevant sides is a variable direct current (graph below).
graph1.JPG (8.17 kB . 504x150 - viewed 10050 times)When one side is nearest to one of the magnets, then the current in that side is zero; when it is in the middle between the magnets, then the current in it is maximal. But since the same applies also to the other side, then for the whole loop we get the graph below:
graph2.JPG (17.72 kB . 504x321 - viewed 10149 times)The resultant current is zero.
I have posted this answer as a further explanation to my assertion that the Faraday’s law of induction is not true. I explain it in detail in "Is Faraday's law of induction true?" https://www.thenakedscientists.com/forum/index.php?topic=78334.0
P.S. It is a well known experiment that when we move a magnet in or out of a solenoid, a current is produced in it. Instead of moving the magnet, we can move the solenoid towards or away from the magnet.
Let’s imagine that the solenoid has a shape of a square. Look at the picture below:
cross sections1.JPG (16.15 kB . 413x255 - viewed 16178 times)The square loop is moving up toward the magnet. Since both sides are moving upward, the current in the right side is away from us, while the current in the left side is toward us. However, if the right side is moving up and the left down (as in the example of the rotating loop), then in both little circles in the drawing above I have to draw the letter x.
Post by: Bored chemist on 26/01/2020 09:26:51
However, generators are known to work. So your assertion that the resultant current is always zero is obviously wrong.
Post by: Hayseed on 26/01/2020 15:13:54
Post by: Origin on 27/01/2020 13:49:06
It's regular currentThat's pretty funny... Thanks for the chuckle.
Post by: Mitko Gorgiev on 05/03/2020 18:26:18
Your diagram, cross sections.jpg, shows why the voltage falls to zero twice per revolution.Your comment shows that you haven't understood anything from what was written.
However, generators are known to work. So your assertion that the resultant current is always zero is obviously wrong.
Post by: Bored chemist on 05/03/2020 19:53:52
Your comment shows that you haven't understood anything from what was written.Well, I'm really quite clever, so what does your observation imply about your communication skills?
Work on them a bit, then come back.
Post by: Mitko Gorgiev on 15/03/2020 07:39:03
However, generators are known to work. So your assertion that the resultant current is always zero is obviously wrong.However, you have admitted that there is an error in the explanation of the working principle of synchronous generators and motors.
https://www.thenakedscientists.com/forum/index.php?topic=78334.msg594180#msg594180
Well, I'm really quite clever ...The others should judge how clever you are.
Post by: Bored chemist on 15/03/2020 09:20:14
However, you have admitted that there is an error in the explanation of the working principle of synchronous generators and motors.No.
I said there's a poorly drawn diagram of it in a textbook.
The actual explanation is the physics, not a picture.
The others should judge how clever you are.They will judge us both.
You claim
The resultant current is zero.And, since generators actually produce current, you are wrong.
I don't need to be very clever to point that out.
Post by: Mitko Gorgiev on 15/03/2020 12:57:46
Well, I'm really quite clever ...Can you solve this physics task? Since you are quite clever, it must be a piece of cake for you.
A single conductor is rotating uniformly in a magnetic field as in the figure below. Can you fill the coordinate system on the right with the waveform of the induced current in the conductor? Please pay attention to the four moments marked with Roman numbers.
[ Invalid Attachment ]
Post by: Bored chemist on 15/03/2020 13:35:01
When you say the induced current, do you mean the induced voltage?
Also, what sort of magnetic field did you imagine?
Are those magnets in the diagram cylinders or cuboid?
Post by: hamdani yusuf on 16/03/2020 10:26:55
A single conductor is rotating uniformly in a magnetic field as in the figure below. Can you fill the coordinate system on the right with the waveform of the induced current in the conductor? Please pay attention to the four moments marked with Roman numbers.(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=78515.0;attach=30383;image)
Using right hand rule, the current should be 0 at point II and IV. Maximum at point I (pointing out of screen). Minimum at point III (into the screen).
Post by: hamdani yusuf on 16/03/2020 10:36:05
P.S. It is a well known experiment that when we move a magnet in or out of a solenoid, a current is produced in it. Instead of moving the magnet, we can move the solenoid towards or away from the magnet.You should notice that the magnetic field working on the left conductor is pointing to down left while on the right conductor it's pointing down right. It's this magnetic field difference which makes difference in electromotive forces generated in either sides of the conductor when it's moving linearly.
Let’s imagine that the solenoid has a shape of a square. Look at the picture below:
(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=78515.0;attach=30065;image)
The square loop is moving up toward the magnet. Since both sides are moving upward, the current in the right side is away from us, while the current in the left side is toward us. However, if the right side is moving up and the left down (as in the example of the rotating loop), then in both little circles in the drawing above I have to draw the letter x.
Post by: Mitko Gorgiev on 16/03/2020 12:23:17
No, Hamdani. You are very, very wrong. Would you try again?A single conductor is rotating uniformly in a magnetic field as in the figure below. Can you fill the coordinate system on the right with the waveform of the induced current in the conductor? Please pay attention to the four moments marked with Roman numbers.(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=78515.0;attach=30383;image)
Using right hand rule, the current should be 0 at point II and IV. Maximum at point I (pointing out of screen). Minimum at point III (into the screen).
Post by: Bored chemist on 16/03/2020 19:03:32
Well, two of us say he's right and you are the only one saying he's wrong.No, Hamdani. You are very, very wrong. Would you try again?A single conductor is rotating uniformly in a magnetic field as in the figure below. Can you fill the coordinate system on the right with the waveform of the induced current in the conductor? Please pay attention to the four moments marked with Roman numbers.(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=78515.0;attach=30383;image)
Using right hand rule, the current should be 0 at point II and IV. Maximum at point I (pointing out of screen). Minimum at point III (into the screen).
Post by: Bored chemist on 16/03/2020 19:08:36
A voltage is induced when the wire cuts through the lines of force.
No voltage is induced when the wire moves along the lines.
[ Invalid Attachment ]
Post by: Bored chemist on 16/03/2020 19:10:56
At I and III the movement of the wire cuts directly across the lines and the voltage is a maximum.
So, Mitko Gorgiev, would you like to explain why you think everybody in the world is wrong, and you are right?
Post by: Mitko Gorgiev on 17/03/2020 13:16:40
So, Mitko Gorgiev, would you like to explain why you think everybody in the world is wrong, and you are right?Do you believe that I do this out of fun - going against the whole world? No, I don't have fun at all. I innerly suffer because of that. But I am deeply convinced that the truth is on my side and I do this solely for the sake of the truth.
......
I have to make a small correction in the things said in my OP, but the essence remains the same.
The waveform of the induced current (it doesn't matter whether I say "induced current" or "induced voltage", since both have the same waveform) in the single rotating conductor will look approximately like this (I say "approximately" because it won't be an ideal half sine function at all):
[ Invalid Attachment ]
I will soon explain in details what this graph means.
Post by: Bored chemist on 17/03/2020 20:16:30
(it doesn't matter whether I say "induced current" or "induced voltage", since both have the same waveform)Please stop posting dross like that. It's true in a single idealised case where the load is a pure resistor.
In the real world, it's wrong.
Do you believe that I do this out of fun - going against the whole world?No, I think you do it out of conceit.
But I am deeply convinced that the truth is on my side and I do this solely for the sake of the truth.And once again
If you are right and everybody else is wrong, how come nobody has noticed?
I will soon explain in details what this graph means.Don't bother; It's wrong, for the reasons I gave earlier.
Post by: Mitko Gorgiev on 19/03/2020 21:07:52
In the second variant (figure b) the conductor is shifted 1 millimeter to the right and is moving again vertically towards the magnet. A current is induced in it which flows away from us.
In the third variant (figure c) the conductor is shifted 1 mm to the left and is moving vertically towards the magnet again. A current is induced in it which flows towards us.
[ Invalid Attachment ]
Consider now this experiment: a straight conductor is moving vertically exactly in the middle between two identical magnets as in the figure (a) below:
[ Invalid Attachment ]
No current is induced in this conductor.
In the figure (b) the conductor is shifted 1 millimeter to the right and is moving again vertically from the lower to the upper magnet. A current is induced in this conductor. But during its movement upwards, the induced current changes the direction. To the dashed line (which is exactly in the middle between the magnets) the induced current flows towards us. When the conductor is exactly in the middle, the current drops to zero. Then, above the dashed line, begins a current flow in opposite direction.
In the figure (c) the conductor is shifted 1 millimeter to the left and is moving again vertically from the lower to the upper magnet. A current is induced in it, but here the reverse happens with respect to that of the figure (b).
Let’s now say that a closed wire loop is moving vertically between the two magnets.
[ Invalid Attachment ]
Through this loop will flow a current, but to the dashed line clockwise, above the dashed line counter-clockwise.
Now the question arises: how come a current is induced in the loop, when there is no change in the magnetic flux during the movement of the loop?
Moreover, why does the induced current change the direction at the dashed line in the middle?
How can these things be explained from the contemporary electromagnetic theory?
I will further elaborate this subject.
Post by: hamdani yusuf on 20/03/2020 09:13:39
Through this loop will flow a current, but to the dashed line clockwise, above the dashed line counter-clockwise.There is indeed change in the magnetic flux during the movement of the loop. BC has drawn the magnetic field between those magnets.
Now the question arises: how come a current is induced in the loop, when there is no change in the magnetic flux during the movement of the loop?
Moreover, why does the induced current change the direction at the dashed line in the middle?
How can these things be explained from the contemporary electromagnetic theory?
(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=78515.0;attach=30391;image)
From the picture above, magnetic flux is least dense halfway between the magnets, hence a loop moving upward from bottom to top will experience high - low - high flux density. The electromotive force is proportional to the flux rate of change, which is initially negative, then zero for a moment where it's in the middle, then positive when closer to the upper magnet.
(https://www.thenakedscientists.com/forum/index.php?action=dlattach;topic=78515.0;attach=30413;image)
Post by: Mitko Gorgiev on 21/03/2020 08:17:19
From the picture above, magnetic flux is least dense halfway between the magnets, hence a loop moving upward from bottom to top will experience high - low - high flux density.Have you heard of homogeneous magnetic field? When the two magnets are close enough, then there is no such thing as "high-low-high".
Besides, how would you apply the Fleming's right hand rule to determine the direction of the induced current in all the variants?
Post by: Bored chemist on 21/03/2020 11:54:19
Have you heard of homogeneous magnetic field?Yes.
The Earth's magnetic field is pretty close to homogeneous over areas that we typically consider in experiments.
But apparently you have not realised this
I still cannot figure out how the Earth inductor contradicts my assertions.
Post by: Bored chemist on 21/03/2020 11:55:10
Besides, how would you apply the Fleming's right hand rule to determine the direction of the induced current in all the variants?In what circumstances do you think Fleming's rule does not apply?
Post by: hamdani yusuf on 22/03/2020 01:41:19
Have you heard of homogeneous magnetic field? When the two magnets are close enough, then there is no such thing as "high-low-high".Yes. I've even demonstrate it in my video about moving magnet. In that case, no electric current is produced.
In your scenario, it can be achieved using magnets with very large diameters. If the magnetic field is truly homogenous, no electric current would be produced.
Post by: Mitko Gorgiev on 27/03/2020 20:11:13
Posting dross, LOL? Your knowledge about electromagnetism is so poor that you don't even know that the voltage and the current in a generator are always in phase, regardless of the character of the load, resistive, capacitive, inductive, whatever!(it doesn't matter whether I say "induced current" or "induced voltage", since both have the same waveform)Please stop posting dross like that. It's true in a single idealised case where the load is a pure resistor.
In the real world, it's wrong.
I apologize to the readers of the forum that I go back to this question, but I have forgotten to answer the know-all to his insults.
Post by: Bored chemist on 27/03/2020 20:47:53
Do you accept that the current is the same?
Do you accept that the current in the capacitor will be out of phase with the voltage across it?
If not, you will need to explain how it's possible.
And, of course, those 3 being true forces you to accept that the current and the voltage in the generator are not in phase.
That's not the only proof that you are wrong, , but its the easy one
Post by: Bored chemist on 27/03/2020 20:52:34
I have forgotten to answer the know-allSays the man who claims that the whole of modern science is wrong.
Post by: Colin2B on 27/03/2020 22:31:28
Your knowledge about electromagnetism is so poor that you don't even know that the voltage and the current in a generator are always in phase, regardless of the character of the load, resistive, capacitive, inductive, whatever!Readers of this forum know you are wrong, and indeed anyone who knows high school physics, and every electricity generating company in the world knows it.
I to the readers of the forum that I go back to this question,
I and many others have done the experiments years ago, done the measurements, and can confirm that you and not @Bored chemist are wrong, very, very wrong.