Electromagnetism and magnetic stuff

[CAT 2]

Homework Statement

Currently I am taking a course that teaches half the material and let's you figure out/ guess the other half. I have been pretty good at succeeding in this so far, but this one has me stumped. It is on my practice test.

What in the world does this diagram mean?

Homework Equations

The Attempt at a Solution

I have the answers to the practice test, and so I know that the following is the correct answer. I just don't understand it.

7

I really want to understand this. From what I have been taught:

a) the v above on the right represents direction of motion.

b) all north poles have a south pole, why do they have no south pole on the right above, but have a north pole. Is the south pole assumed, or did I miss something?

c) The circles on the drawing represent the magnetic field... but they are going in opposite directions. Why?

If someone could just explain this to me, it would be greatly appreciated. Please remember that this is my first year ever doing physics and this is very basic, please write it so that I can understand.

 

[Alloymouse]

a) Yes, you are right.

b) Yes, it is assumed. Magnetic monopoles haven't been proven to exist yet hahaha

c) Refer to Lenz's Law, which states that the induced current in the coil will produce a magnetic field that opposes the motion of the incoming magnet. The "loops" you see are the magnetic field lines produced by the induced current in the coil, so you might want to look that stuff up. In fact, they arent going in the opposite direction - field lines always go from the north pole to the south pole

Feel free to ask for more clarification :)

 

[CAT 2]

Thanks for your answers, they were very understandable! :)
You mentioned they are always going from North pole to South pole; however, above they go in a complete circle around the magnet. Doesn't this mean that they go from North pole to South pole in half a circle and then from South pole to North pole in the other half a circle?

How do I know which direction to place the circles in on a magnet, because in the above magnet the two circles go in different directions, how do I know which direction to put them in?

 

[Alloymouse]

Thanks for your answers, they were very understandable! :)
You mentioned they are always going from North pole to South pole; however, above they go in a complete circle around the magnet. Doesn't this mean that they go from North pole to South pole in half a circle and then from South pole to North pole in the other half a circle?

How do I know which direction to place the circles in on a magnet, because in the above magnet the two circles go in different directions, how do I know which direction to put them in?

With reference to the diagram you have provided, the "completed" part of the loop is merely an indication of magnetic field lines within the magnet, but we should not concern ourselves with that now (as it isn't as simple as the diagram suggests, the loop is to make it look "more complete"); it is more important to understand the external magnetic field for your questions.

The directions of "circles" in the diagram aren't necessarily clockwise or anticlockwise for all cases. For instance, look at this image:

https://www.siyavula.com/read/science/grade-10/magnetism/images/7348b7f2e269d9d94f6541e7fe671eca.png

The north pole is one end of a magnet, and the south is the other end. Hence, you could see it as though all "arrows" (magnetic field lines) come out from the magnet's north pole, and then finding themselves a path to the other end or another south pole. Generally you shouldn't be needing to draw full circles, but rather just arrows (curved or straight) from the north end of a magnet to the south end of the same or another magnet.

Hope this helps :)

 

[CAT 2]

7

So basically, those two circles drawn around the magnet could be in either direction, as long as they are in different directions relative to each other. If the top one was going around ← this way then the bottom one would be going around →this way. But it would be OK if the top one was drawn going around →this way and the bottom one going around←this way. This is possible because both ways have the field traveling from North to South.

And they shouldn't even really be circles, just lines from North to South.

Am I right in this, or is there a standard way that they always go?

I hope this makes sense!

 

[Alloymouse]

And they shouldn't even really be circles, just lines from North to South.

Am I right in this, or is there a standard way that they always go?

I hope this makes sense!

Precisely! Field lines are always north to south.

 

[JordanLau]

Hi, bro, are u a student of ILC, i recently have had some problems with it, can we talk about it together? I am really sorry that i am not a native speaker so that my english is not very good. Here's my Facebook account, thx, bro

 

[rude man]

Gotta be careful.
Given a permanent magnet with N and S poles, the B field points N to S outside the magnet but S to N inside.
Same for a solenoid with N and S poles.