Magnets near a current carrying wire

In summary, the conversation discusses the effects of placing a bar magnet near a current-carrying wire and the differences between this scenario and a solenoid. It is mentioned that the bar magnet will align with the B-field circulating around the wire and that the gradient of the B-field may also affect the motion of the magnet. Further research is suggested to understand how the gradient of a B-field affects a magnetic dipole. The conversation also touches on the differences between the magnet-charge model and the ampere model. Finally, it is concluded that the force acting on a loop of charged particles is proportional to the divergence of the magnetic field.
  • #1
vasya
46
11
Homework Statement
if we place a bar magnet near current carrying wire, will it move in circles?
Relevant Equations
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Hi! I'm trying to understand electromagnetism. So I had a question: if we place a bar magnets on the low friction surface near vertical wire, then switch on the current, what will happen? As I been told they will align with the magnetic lines, and then nothing will happen. I also suggest that they will be bumped a little bit at the moment of turning on the current. But how this situation is different from a solenoid? Solenoid can act as a permanent magnet. But they draw the same magnetic lines in a solenoid and a current carrying wire. It's due to acceleration, right? Can you explain this please?
 
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  • #2
At least tell me if my suggestion is right and magnets will be bumped in direction tangential to a wire in a moment of switching.
 
  • #3
Hint -- In addition to aligning with the B-field that circulates around a current carrying wire, in which direction does that B-field get stronger? Can you think of how that gradient might affect the motion of the bar magnet?
 
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  • #4
in case of a current carrying wire gradient will be stronger near the wire, in solenoid it will will be stronger near the poles. So can you please explain me how gradients affect permanent magnets? Or provide a link to good explanation?
berkeman said:
Hint -- In addition to aligning with the B-field that circulates around a current carrying wire, in which direction does that B-field get stronger? Can you think of how that gradient might affect the motion of the bar magnet?
 
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  • #5
Good. I was just thinking that in addition to the bar magnet aligning with the circulating B-field from the wire, the gradient in the strength of the B-field would cause a different kind of motion of the bar magnet. Maybe do a search to see how the gradient of a B-field affects a magnetic dipole... :smile:
 
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  • #7
now I understand even less than before
 
  • #8
Glad to help!

Er wait...

Did you read the link in my Spoiler post? That gave away the answer sort of...
 
  • #9
Another hint in case it helps while you re-read the Spoiler link -- If I fix one bar magnet on a horizontal frictionless surface and set another bar magnet down on that surface nearby, what happens? (watch your fingers!)
 
  • #10
If we are assuming magnet-charge model, the gradient thing will become clear. If we are talking about ampere model things are not clear
 
  • #11
What are the differences in the B-fields for those two models? Are there gradients in each?
 
  • #12
berkeman said:
What are the differences in the B-fields for those two models? Are there gradients in each?
it will take some time. its 2am in local time, so excuse me for going offline for a while
 
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  • #13
Ok. I got it. There is an imaginary loop of charged particles in each atom of the magnetic material. If we will apply F=qvBsin to every "moving charged particle" inside the magnet everything will become clear. The force acting on a loop of charged particles is proportional to the divergence of magnetic field. It's not about any gradients. Problem solved, at least for now, so thank you, and have a nice day!
 
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FAQ: Magnets near a current carrying wire

1. How does a magnet near a current carrying wire affect the wire?

When a magnet is placed near a current carrying wire, it creates a magnetic field that interacts with the magnetic field created by the current in the wire. This interaction can cause the wire to experience a force, which can result in the wire moving or changing direction.

2. What is the direction of the force on a wire caused by a magnet near it?

The direction of the force on a wire caused by a magnet depends on the orientation of the wire and the direction of the current. The force will be perpendicular to both the direction of the current and the magnetic field created by the magnet.

3. Can the strength of the magnetic field affect the force on a wire near a magnet?

Yes, the strength of the magnetic field can affect the force on a wire near a magnet. The stronger the magnetic field, the greater the force on the wire will be. This is because a stronger magnetic field will have a greater interaction with the magnetic field created by the current in the wire.

4. How does the distance between the magnet and the wire affect the force on the wire?

The force on a wire caused by a magnet near it decreases as the distance between the two increases. This is because the magnetic field from the magnet becomes weaker as it spreads out over a larger area. Therefore, the force on the wire will be strongest when the magnet is closest to the wire.

5. Can a magnet near a current carrying wire affect the current in the wire?

Yes, a magnet near a current carrying wire can affect the current in the wire. This is because the magnetic field from the magnet can induce a current in the wire, causing it to experience a change in its original current. This phenomenon is known as electromagnetic induction.

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