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Repulsion between an electromagnet and a permanent magnet - what is the limit?
Posted 05-29-2024 at 12:43 PM by MalaMan
Back in 2019 I created a thread in the Science subforum of City-Data Forum titled Is there any theoretical limit to the magnetic field strength of permanent magnets?
In that thread I asserted that:
I think this to be a fascinating topic, and I will re-word it to make my point clearer (I hope).
Imagine that an electromagnet made from an air core coil (just a wire without any ferromagnetic or ferrimagnetic core) is placed in direct contact with a permanent magnet. If no electrical current is flowing throw this electromagnet, it won't be atracted by the permanent magnet. There is no attraction between the coil and the permanent magnet because there is no ferromagnetic or ferrimagnetic material used as a core in the coil.
Now, if a electrical current flows throw the electromagnet, it may be attracted or repelled by the permanent magnet, depending on the fact that the magnetic poles of the sides of each magnet that are in direct contact with one another are either the same poles or opposite poles. Remember that same poles repel each other, and opposite poles attract each other.
Suppose the system is arranged in a way that when the current flows throw the electromagnet, the sides of the two magnets facing each other will be the same magnetic poles (it can be easily arranged) and thus there will be repulsion. In this case, if the permanent magnet is fixed to some type of supporting base, while the electromagnet is on some sort of plastic or wooden axis that allows it to freely move horizontally, we will be able to measure how far the eletromagnet moved.
Mechanical energy will be generated in this setup, and measuring the horizontal movement of the eletromagnet is just one possible way of measuring the mechanical energy generated by this magnetic repulsion event.
If the repulsion is strong enough, a very rapid "pulse" of eletricity in the eletromagnet, of just a dozen milliseconds or so, will be enough to create a noticeable horizontal movement.
No, here is the real problem:
Imagine that a setup like the described above is used in an experiment where exactly one volt and one ampere (thus making one watt) of electricity is supplied to the electromagnet during a "pulse" of 20 miliseconds (a second divided by 50), generating mechanical energy and movement of the electromagnet.
What happens if we replace the permanent magnet in the experiment by a stronger one, a permanent magnet with a stronger magnetic field, keeping all the rest of the apparatus as it was?
The answer is rather obvious: more mechanical energy will be generated, because there is stronger magnetic repulsion, even if the pulse of electricity supplied to the electromagnet had the same volts, same amperes and same milliseconds.
So, what is the limit for this?
That's a experimental question I would like to know the answer.
As long as we can build stronger and stronger permanent magnets and use them in this experiment, will we get more and more mechanical energy out of it, keeping the electrical input the same (one volt and one ampere for 20 milliseconds)?
The question stands...
In that thread I asserted that:
Quote:
Given that in a system where an electromagnet made from an air core coil (electromagnet without a ferromagnetic or ferrimagnetic core) is in repulsion against a permanent magnet, the stronger is the magnetic field of the permanent magnet the stronger will be the force of repulsion between the electromagnet and the permanent magnet, with the watts of the direct current (DC) in the electromagnet being kept the same, then the only limit to the mechanical energy output that can be achieved from a rapid pulse of electricity to the air core coil is the theoretical limit to the magnetic field strength of permanent magnets...
Imagine that an electromagnet made from an air core coil (just a wire without any ferromagnetic or ferrimagnetic core) is placed in direct contact with a permanent magnet. If no electrical current is flowing throw this electromagnet, it won't be atracted by the permanent magnet. There is no attraction between the coil and the permanent magnet because there is no ferromagnetic or ferrimagnetic material used as a core in the coil.
Now, if a electrical current flows throw the electromagnet, it may be attracted or repelled by the permanent magnet, depending on the fact that the magnetic poles of the sides of each magnet that are in direct contact with one another are either the same poles or opposite poles. Remember that same poles repel each other, and opposite poles attract each other.
Suppose the system is arranged in a way that when the current flows throw the electromagnet, the sides of the two magnets facing each other will be the same magnetic poles (it can be easily arranged) and thus there will be repulsion. In this case, if the permanent magnet is fixed to some type of supporting base, while the electromagnet is on some sort of plastic or wooden axis that allows it to freely move horizontally, we will be able to measure how far the eletromagnet moved.
Mechanical energy will be generated in this setup, and measuring the horizontal movement of the eletromagnet is just one possible way of measuring the mechanical energy generated by this magnetic repulsion event.
If the repulsion is strong enough, a very rapid "pulse" of eletricity in the eletromagnet, of just a dozen milliseconds or so, will be enough to create a noticeable horizontal movement.
No, here is the real problem:
Imagine that a setup like the described above is used in an experiment where exactly one volt and one ampere (thus making one watt) of electricity is supplied to the electromagnet during a "pulse" of 20 miliseconds (a second divided by 50), generating mechanical energy and movement of the electromagnet.
What happens if we replace the permanent magnet in the experiment by a stronger one, a permanent magnet with a stronger magnetic field, keeping all the rest of the apparatus as it was?
The answer is rather obvious: more mechanical energy will be generated, because there is stronger magnetic repulsion, even if the pulse of electricity supplied to the electromagnet had the same volts, same amperes and same milliseconds.
So, what is the limit for this?
That's a experimental question I would like to know the answer.
As long as we can build stronger and stronger permanent magnets and use them in this experiment, will we get more and more mechanical energy out of it, keeping the electrical input the same (one volt and one ampere for 20 milliseconds)?
The question stands...
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