Magnet is used to levitate another magnet

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Discussion Overview

The discussion revolves around the concept of work in the context of magnetic levitation, specifically whether a magnet levitating another magnet is performing work against gravity and the implications of energy expenditure in this scenario. The conversation touches on theoretical and conceptual aspects of physics related to forces, energy, and the definition of work.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants question whether a magnet levitating another magnet is considered to be doing work against gravity, raising the issue of energy expenditure over time.
  • One participant suggests that the work involved in levitating a magnet comes from the effort to position the second magnet near the first, depending on whether the first magnet is permanent or electrical.
  • There is a contention that if the magnets are stationary, no work is being done, as work is defined by displacement.
  • Another participant acknowledges that while no work is done in the traditional sense, energy is still required to maintain the levitation against gravity.
  • A comparison is made to a book resting on a table, where it is noted that no energy is expended to keep it there, similar to the situation with the levitating magnet.
  • Participants discuss the difference between mechanical work and the chemical energy used by the body, emphasizing that while the body may exert energy, it does not translate to work done on the book or the magnet.

Areas of Agreement / Disagreement

Participants generally disagree on the interpretation of work in the context of magnetic levitation, with multiple competing views on whether energy is being expended and how it relates to the definition of work.

Contextual Notes

The discussion highlights the nuances in the definition of work in physics, particularly in scenarios involving static forces and energy transformations, which remain unresolved.

arul_k
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If a magnet is used to levitate another magnet (using the force of repulsion) can it be considered as doing "work" in opposing the force of gravity? If yes then why does the energy required to do this "work" not diminish over a period of time?
 
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Your scenario is not so clear. I just guess. If a magnet can repulse another magnet (or levitate), it creates some work. But the work comes from you when you try to place the 'another' magnet close enough to the first magnet (in case the first is a permanent one). If the first magnet is electrical, then the work comes from the electricity energy. It is very much like you try to lift a heavy bar up and let it drop, or you press a spring then release it.
 
If the magnets are stationary, then there is no work being done.
 
Zorodius said:
If the magnets are stationary, then there is no work being done.

Yes, I understand that since there is no displacement no work is being done, but there is obvisously some energy being used to keep the magnet levitated and opposing gravity
 
arul_k said:
Yes, I understand that since there is no displacement no work is being done, but there is obvisously some energy being used to keep the magnet levitated and opposing gravity
A book resting on a table is being held against gravity too, but no energy is being expended to keep it there.
 
Zorodius said:
A book resting on a table is being held against gravity too, but no energy is being expended to keep it there.

Yes, but if you were to take the book and hold it up, you would be using energy to do so, not only to lift the book but also to hold it in a fixed position above the table
 
The chemical energy that your body uses to do everyday things is different from the mechanical work that goes on outside your body. From that standpoint, your body is very inefficient. Your body truly is doing no work on that book. Look at the definition of work! w=fd. If there is no distance (no motion), there is no work.
 
russ_watters said:
Your body truly is doing no work on that book.

The key phrase here is "on that book". As you hold the book up, there is activity going on inside your arm muscles, with muscle fibers ratcheting back and forth. Those fibers are doing work which consumes chemical energy and gets transformed into heat, and makes you get tired eventually, but none of that energy gets transferred to the book.
 

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