Something Vexing me about Magnetism and Conservation of Energy

In summary, the superconducting magnet is not breaking the conservation of energy principle, but instead is using a system to channel energy back into the magnet, which will restore the magnetic field and current.
  • #1
Matt Luckham
1
0
Something Vexing me about Magnetism and Conservation of Energy

I have been thinking about an issue at work and it has been bugging me so I thought I would post something on here to see if anyone can explain where my thought process is going wrong.

Say you have a super conducting magnet. It is a big one. The current is switched on and so the magnet becomes active. As it is super conductive the current is not impeded and continues to flow. The magnet is used to lift a large weight off the ground. At somepoint the current is channeled off somewhere else, the magnet stops working and the weight falls. The energy of the weight falling under gravity is captured somehow. The current is channelled back to the magnet, weight is lifted again and so on...

So, my question is, does this system not break the conservation of energy principle? Are we not getting something for nothing here? I am sure I am missing something in my understanding of magnetism, but I thought it was just a field and so no actual mass is lost when it is active?
 
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  • #2
Since the superconducting magnet is lifting a load, it is coupled to it like a transformer. That coupling will limit the current even though you are pushing electrons into a superconducting material. Once the weight stops moving, the superconductor will reach full current flow.
That's my understanding.
 
  • #3
Welcome to PF.

You seem to be under the misconception that a superconducting magnet will not create any restriction to the flow of current. This is not correct: a superconductor has no resistive loss, but it does still obey the laws of inductance.
 
  • #4
I would also offer to keep in mind the large energy EXPENDITURE necessary to keep a superconducting magnet cool enough.
Thus, no matter what one does, the output will never meet or exceed the energy required to keep the system running.
What about hypothetical room temp. superconductors? Ok, we removed the cooling factor but Russ addressed that other factors come into play.
 
  • #5
In other words, the energy conservation still applies.
As the weight potential energy will increase, the magnetic energy will decrease, and so should the magnetic field and the current.
Pulling the weight back will restore the magnetic field.

Losses due to currents induced in the weight should be added to this picture.
 

FAQ: Something Vexing me about Magnetism and Conservation of Energy

How does magnetism relate to the conservation of energy?

Magnetism is a fundamental force of nature that is closely related to the concept of energy conservation. In accordance with the law of conservation of energy, energy cannot be created or destroyed, only transformed from one form to another. In the case of magnetism, energy is conserved through the conversion of electrical energy into magnetic energy, and vice versa. This phenomenon is known as electromagnetic induction and is a key principle in understanding the relationship between magnetism and energy conservation.

Can magnetism violate the law of conservation of energy?

No, magnetism does not violate the law of conservation of energy. As stated previously, magnetism is a form of energy that can be transformed from one type to another, but the total amount of energy in a closed system remains constant. Therefore, the principles of energy conservation still apply to magnetism and its interactions with other forms of energy.

How is energy conserved in a magnetic field?

In a magnetic field, energy is conserved through the interplay between electric and magnetic fields. When a charged particle moves through a magnetic field, the magnetic force exerted on the particle causes it to change direction, resulting in a circular motion. This circular motion requires a constant energy input to maintain, and the energy is conserved as the particle continues to move in a circular path.

Can the conservation of energy be applied to permanent magnets?

Yes, the conservation of energy can be applied to permanent magnets. While the magnetic force of a permanent magnet is always present, it does not require an external energy input to maintain its strength. This is because the magnetic energy is stored within the alignment of its atomic particles, and any external energy applied to the magnet is used to change the direction or strength of the magnetic field, rather than creating it.

How does the concept of energy conservation impact the use of magnets in everyday life?

The law of conservation of energy is a fundamental principle in the design and use of magnets in everyday life. For example, the motors in household appliances, such as refrigerators and washing machines, utilize the conversion of electrical energy into mechanical energy through the use of magnets. Additionally, the energy efficiency of devices and systems can be improved by understanding and optimizing the interactions between magnetism and other forms of energy, ultimately resulting in a more sustainable and cost-effective use of energy.

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