Can the force exerted by a perm magnet be equated to electro magnet watts?

In summary, a permanent magnet does not need to consume any energy to maintain its magnetic field, whereas an electromagnet does.
  • #1
smiddleton
18
0
Hey guys, sorry if this is wrong place to post this. If it is let me and I will try and find the right place. It was the only category where I saw something about energy and physics. This is also probably a basic question but I hope you don't mind me asking.

Let's say you have an electro magnet that takes 10 watts to hold a 10 pound weight for 1 hour and your power supply is a 20 watt hour battery. That means it could hold that weight for 2 hours.

You also have a permanent magnet that can also hold a 10 pound weight for 1 year before its magnetic field decays and the weight drops. Does that mean that one could say that the permanent magnet is outputting the equivalent of 87650 Watt hours to hold that weight for 1 year? I came to 87650 by multiplying 10 watts by the hours in a year.
I hope that makes sense and this isn't a stupid question. Thanks in advance.
SM
 
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  • #2
No, just as a table need not "output energy" to support the objects resting on it.

Electromagnets consume energy because of the electrical resistance in the wires that compose their coils. As current flows through the wires this resistance causes them to heat up, and then this heat energy is radiated away into the surroundings. The energy supplied to the electromagnet goes not into the levitated object, but into this lost heat. No work is done (no energy is transferred) by the magnetic field. It's just that this particular method of maintaining a magnetic field requires constant energy input to maintain the current in the coils.

In contrast, a permanent magnet maintains a magnetic field with no energy input at all--that's what makes it a permanent magnet. If you levitate something with a permanent magnet, no work is being done anywhere (no energy is being transferred).

The key to this is understanding the difference between force and work/energy. Work = force x distance. If you apply a constant force to something that isn't moving, no work is done.
 
  • #3
As The Duck said, an electromagnet might use energy to levitate an object, but it doesn't need to. It's just an inefficient electromagnet. You could go out and get a better one, perhaps made with superconductors, and it wouldn't need any energy input at all.

Likewise, a helicopter uses energy to hover in place, but it doesn't need to. You could easily replace the spinning rotor blade and thousands horsepower engine with a table, for example. Of course you'd then be stuck in place and the helicopter would be useless, but the point remains.
 
  • #4
Thanks Duck, and Lsos for the replies. They make a lot of sense. I am trying to get a good grasp on this stuff.
 
  • #5


I would say that the force exerted by a permanent magnet cannot be equated to electro magnet watts. While both magnets produce a force, they operate on different principles and cannot be compared in terms of watts.

The watt is a unit of power, which is the rate at which energy is transferred or used. In the case of an electromagnet, the power consumption is directly related to the strength of the magnetic field and the amount of time it is applied. However, in a permanent magnet, the magnetic field is constant and does not require any external power source to maintain it. Therefore, the concept of watts does not apply to a permanent magnet.

Additionally, the force exerted by a permanent magnet is not constant and will decrease over time as the magnetic field decays. This is different from an electromagnet, where the force can be adjusted by changing the amount of power supplied to it.

In conclusion, while both magnets can exert a force, they operate on different principles and cannot be compared in terms of watts. The force exerted by a permanent magnet cannot be equated to electro magnet watts.
 

1. Can a permanent magnet and an electromagnet exert the same amount of force?

No, the force exerted by a permanent magnet and an electromagnet are not equivalent. The strength of a permanent magnet depends on its material and shape, while the strength of an electromagnet depends on the current flowing through it.

2. How is the force exerted by a permanent magnet different from that of an electromagnet?

The force exerted by a permanent magnet is due to its magnetic field, while the force exerted by an electromagnet is due to the interaction between its magnetic field and an external magnetic field.

3. Can the force exerted by a permanent magnet be measured in watts?

No, the force exerted by a permanent magnet is typically measured in units of Newtons(N) or pounds(lbs). Watts (W) is a unit of power, which is the rate at which work is done, and is not directly related to force.

4. Is the force exerted by a permanent magnet stronger than that of an electromagnet?

It depends on the strength of the permanent magnet and the current flowing through the electromagnet. In general, a permanent magnet will have a stronger force, but an electromagnet can be made stronger by increasing the current.

5. Can the force exerted by a permanent magnet be turned on and off like an electromagnet?

No, the force exerted by a permanent magnet cannot be turned on and off like an electromagnet. A permanent magnet has a constant magnetic field, while an electromagnet's magnetic field can be controlled by the current flowing through it.

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