Deduction about Magnetic Poles surrounding a Conductor

[haruspex]

the magnetic field will point in the direction of the net electric field

Did you mean that?

Several things bother me about the question. I did wonder if it has been accurately worded in post #1, but at https://www.knowledgeboat.com/quest...wo-stretched-copper-wires--711181432220828700 I see exactly the same wording. I also see that the official-looking answer given there claims it does not matter which is which of the poles, merely that they be different. That's a stronger statement than in post #1, and seems extremely unlikely.

It also bothers me that we are not told the circuit is horizontal, that the F arrow looks like it is in the plane of the circuit, that it is shown as acting on the rod, and that it is not entirely clear whether the wording refers to the force on the rod or the force on the poles.

Finally, what is the significance of stretched wires versus a thick rod? It's the same current all the way around. Am I missing something?

 

[Delta2]

Did you mean that?

Several things bother me about the question. I did wonder if it has been accurately worded in post #1, but at https://www.knowledgeboat.com/quest...wo-stretched-copper-wires--711181432220828700 I see exactly the same wording. I also see that the official-looking answer given there claims it does not matter which is which of the poles, merely that they be different. That's a stronger statement than in post #1, and seems extremely unlikely.

It also bothers me that we are not told the circuit is horizontal, that the F arrow looks like it is in the plane of the circuit, that it is shown as acting on the rod, and that it is not entirely clear whether the wording refers to the force on the rod or the force on the poles.

Finally, what is the significance of stretched wires versus a thick rod? It's the same current all the way around. Am I missing something?

Yes the statement has issues but I think you are being a bit pedantic.

The core issue is that what is seems to be the official answer claims that the poles need just to be different which doesn't seem entirely correct to me.

 

[haruspex]

Yes the statement has issues but I think you are being a bit pedantic.

It is so sloppy I have no confidence that the question setter is adequately qualified.

 

[kuruman]

Did you mean that?

No, it was a typo that is now fixed. Thanks for the catch.

 

[kuruman]

First I will iterate that this is not a well-posed question. However, after some thought, I think I understand what it's about. An important clue is the passage "What should be the magnetic poles at points A and B lying on either side of the conductor $\dots$" Assuming that the author of the problem knows that magnetic monopoles do not exist, we have to consider that the aforementioned "poles" can be ends of bar magnets between which the conducting rod is placed. Note that the direction of the current in the rod is known and fixed.

There are two configurations of placing the rod between the "poles" around the rod, in attraction (figure below left) or in repulsion (figure below right). The direction of the current is out of the screen in both cases. The direction of the force on the rod (green arrow) can be found using the right hand rule. In each case I placed the rod in a region where the external magnetic field is mostly in one direction. Note that when the poles are in attraction, the force is perpendicular to the line joining A and B, but when they are in repulsion, the force is parallel to that line.

 

[Darshit Sharma]

Yes the statement has issues but I think you are being a bit pedantic.

The core issue is that what is seems to be the official answer claims that the poles need just to be different which doesn't seem entirely correct to me.

That is not an official answer tho. These websites just merely publish solutions to question papers which in most cases are wrong and misleading. Even some books too. I am so frustrated with all this. Even the SNOW and AMPERE SWIMMING RULE some webs and teachers use are just wrong.

Actually the council didn't publish an official board exam answer key last year. I will be appearing for the board exams in Feb.