THE CONTENT OF THIS PAGE WILL BE UPDATED AND IMPROVED WITH SOME CORRECTIONS IN THE FUTURE BOOK RELATED TO THE ELECTRIC CURENTS AND ELECTROMAGNETIC WAVES
THE ,,TEN EURO” EXPERIMENTS
A simple circuit reproducing the Oersted experiment (fig 1.) is made using first time an unisolated conductor (L), a source and a magnet needle. When the switch is closed, thus causing an electric current to flow in the conductor, the magnetic needle placed near the conductor is deflected. As soon as the current stops flowing, the needle returns to its original position.
If the direction of the current is reversed, the needle is deflected in the opposite direction. It is well known the influence of electric current over the magnetic needle.
In second step change the conductor L successively with:
• a semiconductor bar - a galena material type is more available;
• a tube gas at low pressure;
• an ionic conductor – a NaCl solution is easy to obtain and the processes of electrodes are not so important for experiment.
In case of tube gas there is necessary a higher potential in order to have an electric current flowing through circuit.
When the contact is switch on, in case of these modified Oersted experiments, the magnetic needle remain undeviated from N-S direction. Contrary to actual electromagnetism which postulate that an electric current produce a magnetic effect, in case of electric current passing through gases, semiconductors, or solution, the magnetic effects are some order of magnitude smaller in comparison with metallic conductor. If the polarity of source is changed, again no influence of electric current over the magnetic needle is observed. Where is the error?
Figure 1. Oersted experiment
There is no explanation in actual electromagnetism, for the presence of magnetic field around conductors in case of the metallic conduction, and the absence of the same magnetic field in case of other types of conduction.
This experiment suggests a correlation between conduction type and magnetic properties and in this book a qualitative explanation of these phenomena will be presented.
The experiment scheme is presented in fig 2 and resides in a series circuit formed by a battery of 1,5 V, a cup of water, and a miliampermeter.
For the beginning put distilled water in the cup and observe the indication of ampermeter. Normally the distilled water must be insulator; the value of intensity is very low, close to zero, depending on the water purity.
Now put a little bit kitchen salt in the water and observe the effects. The indication of ampermeter modified significantly. Leave the current to pass through instrument a little bit time and note the current intensity after different moments of time. Normally the value remain constant with small decreasing after long time due to the exhausts of battery (this can be prevent using a stabilized source at 1,5 V). For more economical budget switch the ammeter with your tongue and use only a normal battery of 1,5 V. In case of distilled water your tongue will not feel the electric current. When the salt is added to the solution the tongue will feel the circulation of electric current.
This is a banal experiment made at low level teaching physics and probably you will ask: what’s the trick?
Figure 2. Experiment design
We know that salt solution permits to electric current to pass through, and this is due to the ions which travel toward electrodes and chemical reactions take place at electrode-solution interface. But what’s happened if the ions have not the possibility to react at electrodes and to change the electrons? From electrochemistry we know that for water electrolysis are necessary more then 1.7 Volts, and for NaCl electrolysis approx. 4 Volts. In our experiment the voltage is lower than value necessary for electrode reactions and for electron transfer, fact confirmed also visually, because no reactions are observed at electrodes. In this case according to actual physics the ions must migrate to electrodes and at beginning the intensity must be great due to the movement of charges in solution; in time around the electrodes are formed charged regions (fig 3.) and intensity of electric current must decrease like in fig 4, admitting a constant velocity of ions in solution. After a time interval the intensity of electric current must became zero and the solution transforms in a capacitor in this conditions.
Figure 3. Ions circulation in solution
Figure 4 Expected variation of current intensity
The reality is opposite; with a stabilized source, the intensity of current remains indefinitely constant in time. The accumulation of charge around the electrodes and capacitor comportment of solution is not observed in these conditions of experiments.
Again there is no possible explanation in electrodynamics.
The circuit is the same like in experiment 2; change only the source (preferable DC source) and a vat of larger dimension for water. Better a vat with rectangle form, one dimension being at least 10 times the other dimension. Chose a voltage up to 60 V and check the intensity to be up to 20 mA. Then put a finger in the vat in opposite side of electrodes position and switch on K. The sensation is not so pleasant, but is quite instantaneous.
According to actual electrodynamics your sensation is not a reality. Because, the electric current is formed by a flux of electrons flow between electrodes, so it is impossible to flow in the other part of the vat. If some electrons will dare to adventure in this direction their velocity are insignificants so you must wait minutes or hours in order to be knocked by an electron and to feel something.
Figure 5. Experiment 3 design
Again no explanation from electrodynamics.
Take an old TV set and put in front of him an aluminum metal foil (available in any supermarket) connected to an ammeter and to null point like in fig. 6. It’s better to stick the foil on the external part of tube and to cover a greater part of the screen. Start the TV and watch the indication of ampermeter. Normally the electrons emitted by tube are accelerated at 27-30 kV. A part of them hit the metallic foil and flow through ammeter forming an ,,electric current”. But the ammeter refuse to show any expected indication. Disconnect the ampermeter and leave the electric charge to pass through your body (put one hand on a conductor and other to the other conductor). Normally a flux of electrons (an electric current in actual conception) flow through your finger from metal sheet to the null point but you feel nothing. Compare the situation with the previous experiment when no electrons are passing through your finger.
Figure 6. Experiment 4 design
If you disconnect the ampermeter and put a voltmeter connected to the metal sheet and to null point a difference of potential is always registered due to the difference of electrostatic charge of foils and null point.
What is the meaning of electric current?
A simple circuit reproducing the Faraday induction experiment (fig. 6) is made.
Figure 6. Faraday experiment
At beginning repeat the experiment of Faraday. When the magnet is moving toward or back relative to the metallic conductor L in the ammeter a small electric current is registered.
In the second step replace the metallic conductor L with an ionic conductor (a vat with NaCl solution) and repeat the experiment. It is necessary to make some adaptation for vat in order to perform the experiment. Taken into consideration the direction of ions movement in magnetic field inside the vat, two walls of the vat are covered with a metallic foil and further to an ammeter like in fig 7.
When the magnet is moving toward or back relative to the vat, the ammeter does not indicate the apparition of a current pulse. Repeat the experiment with a higher concentration of salt and a powerful magnet. Repeat the experiment with different directions of magnet relative to the electrodes. The results are the same more precisely absence of an electric current when ions are moving in solution in presence of a magnetic field.
Figure 7. Modified Faraday experiment
To date electric current is defined like a charge movement. Of course related to the experiment the speed of electrons is considered higher then speed of ions in solution. In the same time it’s necessary to take in consideration that in metallic conductor only electrons are moving but in the solution positive and negative ions are freely to move. Even admitting a lower speed for ions relative to electrons with actual techniques we should be able to evidence a small electric pulse when the magnet is moving relative to the vat.
There isn’t a plausible explanation of this experiment in actual electrodynamics.
Reading this book you will discover the answers to these simple macroscopic experiments with roots in atomic world.