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Q: a solenoid with ends marked a and b is suspended so that the core can rotate in the horizontal plane. A current is maintained in the coil so that the electrons move clockwise when viewed from end A towards end B. How will the coil align itself in earth's magnetic field?

Now An answer I have (from an answer bank our teacher gave us) is "end A will point towards the geographic south pole."

Meaning that end A becomes the south pole of the magnet. Now I don't understand how.

Since the question says that the electrons move clockwise when viewed from end A, so that means the conventional current moves counter-clockwise when viewed from end A. If we apply the right hand rule for solenoids ( or atleast the version my book has: the way our fingers curl is the current's direction and our thumb is the field's), when you look from end A towards end B the field is directed towards you, making end A the north pole of the solenoid. Right...?

Any help is appreciated.

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Your reasoning is sound and (if I may say so) very nicely presented. End A is indeed the North pole of the solenoid. 'North", in this context, is short for "North-seeking", which means geographically North-seeking. So unless we've both done something silly, the answer you've been given is wrong.

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  • $\begingroup$ Thanks for the compliment. I thought I had made a mistake at first as well but looks like the mistake is on the book's end $\endgroup$
    – Dahen
    Oct 13, 2017 at 11:07

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