Identifying Magnetic Interactions

In summary, the Homework Statement states that there are two problems with homework: determining the direction of the net force exerted by the magnet on the wire segment at the instant that the magnet is in the position shown and finding the current through the wire. In the Attempt at a Solution, the first problem is solved using Newton's Third Law and the second problem is solved by drawing the currents around all three wires using the right-hand rule.
  • #1
jlmccart03
175
9

Homework Statement


There are two problems:

1. At the instant the switch is closed determine the direction of the net force exerted by the magnet on the wire segment at the instant that the magnet is in the position shown. Explain.

2b. Suppose the a third wire, carrying another current i0 out of the page, passes through point P. Draw a vector on the diagram to indicate the magnetic force, if any, exerted bon the current in the new wire at P. If the magnitude of the force is zero, indicate that explicitly. Explain your reasoning.

Homework Equations


I don't think there is any relevant equations since this is all theoretical actions.

The Attempt at a Solution


For problem 1 I didn't know how to go about it so I used Newton's Third Law. In the previous part they wanted me to find the direction of the current through the wire and by using the right-hand rule I found the current to be ccw so the B-field must point toward the magnet. Now using Newton's Third Law I said that since there must be an equal and opposite force then the net force exerted by the magnet must be towards the wire or the opposite direction of the B-field produced by the wire. Is this reasoning correct? I feel like the wire should have a net force to the right allowing it to be repulsed by the B-field.

For problem 2 I drew the currents around all three wires using the right-hand rule and immediatly got confused on how to determine the direction vectors. I want to say it will be straight down since the left wire will cancel out with the right wire thus leaving only the top wire to exert a magnetic force.

Any help would be great!:smile:
 

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  • #2
jlmccart03 said:
Newton's Third Law
I'd have used Lorentz !
jlmccart03 said:
right-hand rule I found the current to be ccw
Connecting a battery to a loop has little to do with the right-hand rule. Current flows from high voltage to low voltage. If the picture of the battery is halfway realistic, the positive side is at the top.
 
  • #3
BvU said:
I'd have used Lorentz !
Connecting a battery to a loop has little to do with the right-hand rule. Current flows from high voltage to low voltage. If the picture of the battery is halfway realistic, the positive side is at the top.
Ok if current flows positive to negative then in this example the B-field is in and the current is clock-wise. I have not learned Lorentz's Law yet and am a bit confused cause I know there is a qv x B, but where does the qE come from. And how do I use it to determine the direction only?
 
  • #4
Let's make one step back. From the text that you could easily have rendered in the full problem statement but cut off partly in a picture, I can read :
...ung by a string and then placed near a wire as shown. When the switch is closed
...ates such that the ends of the magnet move as indicated by the arrows
...
... the switch is close determine:

[edit]wrong button. If the magnet ...ung by a string moves as the arrows indicate, which way is the magnetic field inside the current loop ?
I think I start to understand your
jlmccart03 said:
In the previous part they wanted me to find the direction of the current through the wire and by using the right-hand rule I found the current to be ccw
And I am inclined to agree (provided that what I telepathize is indeed your exercise -1) which would mean the battery picture is mischievously misleading and the top is the negative side.

Can you enlighten us ? I understand you want to go along with exercise 1 and 2 but we want to be sire we are on the same path and that it's the right path ...


But now I don't know how to interpret
jlmccart03 said:
the B-field must point toward the magnet
Great. What does that mean ?
 
Last edited:
  • #5
BvU said:
Let's make one step back. From the text that you could easily have rendered in the full problem statement but cut off partly in a picture, I can read :[edit]wrong button. If the magnet ...ung by a string moves as the arrows indicate, which way is the magnetic field inside the current loop ?
I think I start to understand your

And I am inclined to agree (provided that what I telepathize is indeed your exercise -1) which would mean the battery picture is mischievously misleading and the top is the negative side.

Can you enlighten us ? I understand you want to go along with exercise 1 and 2 but we want to be sire we are on the same path and that it's the right path ...


But now I don't know how to interpret
Great. What does that mean ?
Ok I uploaded an image of the entire first problem with my reasoning to the first problem already written there. I want to believe based on the image that the current is ccw and thus there is a B-field into the page. (Hard to describe through words). Based on that observation then I wanted to believe that there would be a net force from the magnet to the left pointing toward the wire since the wire would exert a force to the right at that position, but I am really now just confused on what the overall problem is looking for me to do.
 

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  • #6
Your description looks reasonable. To solidify your understanding you might google: "Oersted experiment"
 
  • #7
gneill said:
Your description looks reasonable. To solidify your understanding you might google: "Oersted experiment"
So how do I go about solving for part 2 on the net force? Is it toward the wire or not?
 
  • #8
jlmccart03 said:
So how do I go about solving for part 2 on the net force? Is it toward the wire or not?
The question asks for the direction of the net force exerted by the magnet on the wire. So of course any force exerted on the wire must act towards the wire. But "towards" does not come with any particular direction. To get your answer, look at the motion that the magnet is going to make. What kind of force or forces must act on the magnet to make that happen? Then think about Newton's Third Law.
 
  • #9
gneill said:
The question asks for the direction of the net force exerted by the magnet on the wire. So of course any force exerted on the wire must act towards the wire. But "towards" does not come with any particular direction. To get your answer, look at the motion that the magnet is going to make. What kind of force or forces must act on the magnet to make that happen? Then think about Newton's Third Law.
I figured it out by using F=qv x B and the fact that qv is The current I. I then did right and rule and it's basically into the page but kinda angled due to the image but if it was front faced the force would be into the page. So how do I go about doing the second problem?
 
  • #10
jlmccart03 said:
So how do I go about doing the second problem?

You should know that we generally do not allow multiple separate problems in a single thread. This is to avoid having the confusion of separate discussions taking place at the same time. It would be preferable for you to start a separate thread for the second problem.
 

1. What is a magnetic interaction?

A magnetic interaction is the force that acts between two or more magnetic objects or particles. This force is caused by the presence of magnetic fields, which are created by the movement of electric charges.

2. How do you identify magnetic interactions?

Magnetic interactions can be identified by observing the behavior of objects in the presence of a magnetic field. If the objects are attracted or repelled by the magnetic field, then a magnetic interaction is present.

3. What are some common examples of magnetic interactions?

Some common examples of magnetic interactions include the attraction or repulsion between magnets, the movement of a compass needle in response to the Earth's magnetic field, and the way iron filings align in the presence of a magnet.

4. How do magnetic interactions affect everyday life?

Magnetic interactions have many practical applications in everyday life. They are used in technologies such as electric motors, generators, and MRI machines. They also play a role in the Earth's magnetic field, which protects us from harmful solar radiation.

5. Can magnetic interactions be manipulated?

Yes, magnetic interactions can be manipulated by changing the strength or direction of a magnetic field. This is how technologies such as electric motors and MRI machines work. Scientists and engineers are constantly finding new ways to harness and control magnetic interactions for various purposes.

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