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Author Topic: Magnetic effects around electric currents cut off experiment  (Read 4010 times)

Offline sorin cezar

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Please, before commenting the post,  read at least the experiment  and also the book Currents, fields and particles written by Francis Bitter, 1956, MIT. Also the other book used as reference in the text is fine ....
People are giving advices how to connect two cables or how to use a isotopic source but they have forgotten to read some scientific literature...


Experiment:   Electric current around ionic conductor
Let’s consider a circuit like in fig. 1 formed by a DC source, an ionic conductor, and a metallic conductor with the same section like ionic conductor. The length of PM side is about 40 cm and both metallic conductor and ionic conductor present the same length and the quite the same transversal section. The ionic conductor is made by a sectioned tube with an appropriate volume of liquid (see an increased view of transversal section in fig. 1). For the simplicity of interpretation, the experiment is made with a KCl solution (both ions have quite the same mobility in solution).
 
Figure 1. Electric current measurement
As far the electric current into a circuit containing a solution is smaller due to the resistance opposed by solution, a powerful DC source is needed. With a source able to deliver at least 12 V and 3 A, the magnetic effects around PM portion of the circuit are observed using a common magnetic needle. In case the ionic conductor is made by a circular plastic tube, the current must be even greater because magnetic field around ionic conductor is shielded by the plastic tube.
In our experiment magnetic effects are observed for both portion of metallic and ionic section of circuit (the magnetic needle is perturbed from its N-S alignment and rotates in conformity with direction of electric current delivered by DC source).
Let us change the solution with a sulfuric acid solution. In this case, from electrochemistry, we know that mobility of proton (cation) is much higher then mobility of sulfuric species). Even in this case, the magnetic field around ionic conductor has the same direction like the magnetic field around metallic part.
Even another possibility, let us consider a solution of KOH as electrolyte. In this case the mobility of hydroxyl anions is 3 times bigger then mobility of potassium cation. Again, the magnetic field around ionic part of circuit keeps the same direction like the magnetic field around the metallic part of circuit.   
The obtained results seem to be in agreement with other replications of this experiment. As comparison a similar experiment described in a well known experimental book - Chemical Demonstrations, (vol IV, Bassam Shakhashiri, Chapter 11.1. - Magnetic field from a conducting solution) is presented below:
….Place the transparent magnetic compass on the overhead projector. Lay the copper wire over the compass and align it so that it is parallel with the compass needle. Clip one of the leads from the battery to one end of the wire. Touch the other led to the other lead of the wire. When contact is made, the compass needle will rotate until it is perpendicular to the wire. Remove the lead from wire and the needle will return to the prior positions. Unclip the battery lead from the one end of the wire and reattach to the other end of the wire. Touch the second lead to the opposite end of the wire. This time the compass needle will rotate in the opposite direction to become perpendicular to the wire. Disconnect the battery and the compass needle will return to its original position. Remove the wire from the projector.
Set the stand holding the tube of 2M H2SO4 on the overhead projector. Align the horizontal section of the tube so that it is parallel with the needle immediately over the compass. The bottom of the tube should be touching the top of the compass. Connect one lead from the 12 V power supply to one of the electrode in the tube. With the power supply turned off, connect the other lead to the other electrode. Turn on the power supply. The compass needle will immediately turn until it is perpendicularly to the tube. Turn off the power supply. The compass needle will return to its original position. Reverse the connection of the power supply. The compass needle will rotate in opposite direction to become perpendicularly on the tube . Turn off the power supply and the needle will return to its original position…..

Discussion:
This demonstration shows one of physical effects of the passage of an electric current, namely, an electric field.
The flow of electric current produces a magnetic field, weather the current flows through a metallic conductor in the forms of electrons or through an electrolyte solution in the forms of ions.
The magnetic field is detected in this demonstration with a magnetic compass. When the needle is placed in a magnetic field, it aligns itself parallel with the field. In absence of the other fields, the earth’s magnetic field causes the needle to align it self in a north south direction.
The connection between electric current and magnetic phenomena was observed in 1819 by Oersted. He saw the same effect shown in this demonstration that a magnetic needle moved when an electric current flowed through a nearby wire.
A moving electric charge generates a magnetic field. This magnetic field will interact with any other magnetic field. All atoms contain moving charges, namely, the electrons that surrounds the nucleus.
When a compass is placed in a magnetic field, the needle aligns itself with the field. Because Earth has a week magnetic field orientated along its axis of rotation, a compass usually align to this axis unless the compass is placed in a field stronger then that of earth.
In this demonstration the compass is placed in a magnetic field created by an electric current flowing in North South direction. When a current flows in the wire the magnetic compass rotates out of the north south alignment. This indicate that magnetic field created by electric current is greater then earth magnetic field, and has another direction, more precisely, the field is perpendicular on the direction of current flow. The direction in which the compass needle turns also depends on the direction on current flows.
The compass needle deflects when a voltage is applied between electrodes in a nearby solution. This indicates that electric charges are moving into the solution. These moving charges are ions: positive hydrogen and negative sulfate.
The electric conductivity of an electrolytic solution is not as great as that of a metal. Therefore, the voltage applied between the electrodes must be greater then that applied to the wire, in order to produce a similar electric current in the two conductors.
In spite of the higher voltage, the current in the solution is likely to be only a tenth of that in the wire. The weaker current in the solution will produce a weaker magnetic field, so the compass needle may not rotate as far or as quickly as it does near the conducting wire. This causes the magnetic field produced by the current in the solution to be more diffuse that near the wire. This too will contribute to a less dramatic rotation of the needle. Therefore it is necessary to place the tube of conducting solution as close to the compass needle as possible.
When current flows through a solution, two types of conductions occur. In the solution, the movement of ions conducts the electric current. Sulfate anions move in one direction and hydrogen ions move in opposite direction. In the wire connected to the electrons and in electrodes the current is conducted by moving electrons. At the surface of electrodes, the current changes from electron carried to ion carried. This transformation is possible only if all electrons are added or removed from ions.
Such addition and removal from ions result in chemical transformation


What a nice presentation,  but what an absurd interpretation …..
For simplicity, I will start with expected result when a KCl solution is used in ionic conductor. As far the mobility of K species (0.000670) is quite the same like mobility of chlorine species (0.000678), their opposite movements will have as result a null magnetic effect (fig. 2). It is simple and straightforward as plus 2 and minus 2 gives a null result. As consequence there should be a magnetic field around metallic part of circuit but not a magnetic effect around ionic portion of circuit.

 
see fig in the attach
Figure 2. Charge displacement inside metallic and ionic conductor

What should happen when a sulfuric acid solution is used in ionic conductor?
In this case, as far hydrogen positive species moves faster then sulfuric species, the magnetic field around ionic portion of circuit must be opposite ( at least for a period of time) to the magnetic field around metallic portion of circuit. No such effect was ever observed…

fig in the attach
 
Figure 2. Charge displacement inside metallic and ionic conductor

The experimental results rule out completely the actual interpretation for ionic effect of charges movement. If after a time interval the speed of both cations and anions becomes equal, there is an overlap with previous situation ….

What should happen when KOH solution is used as ionic conductor?
In this case the mobility of potassium species is smaller then mobility of hydroxyl species and the magnetic field around the conductor keeps the same orientation like that around the metallic part, only its size has to be diminished….
Only this part of the theory has the tendency to fit to the experimental results. But if we analise the quantitative aspects even this part of the experiment cannot be explained by actual electromagnetism ...

How can we interpret the experiment though ?

Who is responsible for the magnetic field arround ionic conductor ...
« Last Edit: 02/11/2013 13:44:52 by sorin cezar »


 

Offline alancalverd

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magnetic field around ionic conductor is shielded by the plastic tube.

Wow! What plastic are you using? Can I get some to shield my MRI machines?

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This demonstration shows one of physical effects of the passage of an electric current, namely, an electric field.

but you have been using magnetic field detectors

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As far the mobility of K species (0.000670) is quite the same like mobility of chlorine species (0.000678), their opposite movements will have as result a null magnetic effect (fig. 2). It is simple and straightforward as plus 2 and minus 2 gives a null result. As consequence there should be a magnetic field around metallic part of circuit but not a magnetic effect around ionic portion of circuit.

No. The ions move in opposite directions because they are carrying opposite charges, so the net current is in the forward direction: a positive charge moving left to right is equivalent to a negative charge moving right to left.  Same applies to the sulfuric acid transient you mention later.

Don't confuse the electromagnetic effect with the Hall effect, which does depend on the charge sign of the carrier!
« Last Edit: 02/11/2013 16:47:18 by alancalverd »
 

Offline SimpleEngineer

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"The electric conductivity of an electrolytic solution is not as great as that of a metal. Therefore, the voltage applied between the electrodes must be greater then that applied to the wire, in order to produce a similar electric current in the two conductors.
In spite of the higher voltage, the current in the solution is likely to be only a tenth of that in the wire. "

Tbh as with your other discussions, your words show your lack of understanding of electricity.

V=IR  -> the more resistance the lower the current for a fixed Voltage. So its not 'inspite' of the higher voltage its 'because' the conductivity is significantly lower in the solution than it is in the wire.

Magnetic field density is directly proportional to current density (with mass/charge density being 3 orders of magnitude greater in ions) you would have to be looking at much larger voltages to achieve the same magnetic fields.. so my interpretation is.. you are not generating a large enough magnetic field to be detected over that of the earth.
 

Offline sorin cezar

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magnetic field around ionic conductor is shielded by the plastic tube.

Wow! What plastic are you using? Can I get some to shield my MRI machines?

No. The ions move in opposite directions because they are carrying opposite charges, so the net current is in the forward direction: a positive charge moving left to right is equivalent to a negative charge moving right to left.  Same applies to the sulfuric acid transient you mention later.


I was pointing that response of ionic conductor is delayed and less evident when you use a entire tube instead of a section . As far when I made the experiment I did not have an magnetometer, the experiment is only qualitative ..
It will be repeated using a magnetomer...!

Please stop telling rubbish...
Ions moves in different direction and an electric current goes forward... after what manual have you learned science?
How does the courrent moves forward... there is a macroscopic tunel effect and electrons jumps through solution from an electrod to another..?

"The electric conductivity of an electrolytic solution is not as great as that of a metal. Therefore, the voltage applied between the electrodes must be greater then that applied to the wire, in order to produce a similar electric current in the two conductors.
In spite of the higher voltage, the current in the solution is likely to be only a tenth of that in the wire. "

Tbh as with your other discussions, your words show your lack of understanding of electricity.

V=IR  -> the more resistance the lower the current for a fixed Voltage. So its not 'inspite' of the higher voltage its 'because' the conductivity is significantly lower in the solution than it is in the wire.

Magnetic field density is directly proportional to current density (with mass/charge density being 3 orders of magnitude greater in ions) you would have to be looking at much larger voltages to achieve the same magnetic fields.. so my interpretation is.. you are not generating a large enough magnetic field to be detected over that of the earth.

The experiment is carried out in such condition that what you  are writing is completely irrelevant...
As far on a portion of metallic circuit I have a deflection of magnetic needle, and I have deflection on the ionic part... it means in entire circuit, there is an electric current generating an magnetic effect greater then earth magnetic field.
The problem is you did not understood the topic of the experiment...
The topic was in few words: using different solutions with different  mobilities for ions, I should have different effects arround the ionic conductor ...and this did not happen .

 
« Last Edit: 05/11/2013 10:46:24 by sorin cezar »
 

Offline alancalverd

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I was pointing that response of ionic conductor is delayed and less evident when you use a entire tube instead of a section .

Not in this universe. The appearance of a magnetic field is always instantaneous when a current flows.

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Ions moves in different direction and an electric current goes forward.

Exactly the point. A positive charge  moving to the right has the same effect as a negative charge moving to the left. This is the principle upon which every semiconductor device (except a Hall effect magnetometer) works. It is you, my friend, who is talking rubbish.
« Last Edit: 05/11/2013 15:56:03 by alancalverd »
 

Offline SimpleEngineer

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You should really read the content of posts before thinking you are right.

the Magnetic field density is directly proportional to current intensity the current density is metals is several orders of magnitude higher than the current density in solutions (electrons have significantly less mass than ions, so the charge density is MUCH higher)

To get a similar magnetic field generated by the solution you would need orders of magnitude of current to achieve the same magnetic density. 
 

Offline sorin cezar

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You should really read the content of posts before thinking you are right.

the Magnetic field density is directly proportional to current intensity the current density is metals is several orders of magnitude higher than the current density in solutions (electrons have significantly less mass than ions, so the charge density is MUCH higher)

To get a similar magnetic field generated by the solution you would need orders of magnitude of current to achieve the same magnetic density. 

Simple engineer, in the proposed experiment I make the comparison between different parts of the same circuit...
Are you telling me that current in solution is different as value from the current in the cable nearby?
 

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