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Homework Help: Creative Questions on Magnetism

  1. Jun 2, 2007 #1
    1. The problem statement, all variables and given/known data
    Question 1- Magnetized Ship
    You are standing on a shore beside a shimmering blue sea. You will go on a sea expedition to Magnesia and claim the lost treasure of Magnesia. Magnesia is an island which lies near the Antarctica. The only way to get there is by sea. The ship that is given to you is a giant ship but the propulsion system is out of order. Someone suggested magnetziing the ship so that it has a south seeking magnetic pole. The ship will then naturally move along the Earth's magnetic field.

    Too bad the idea won't work. Can you explain why? (3 Marks)

    Question 2- Mysterious Cutlery
    Luckily someone reapirs the propulsion system and now you can begin your expedition. The ship has been moving speedily and steadily. Unexpectedly storm clouds begin to gather ominously and lightning can be seen flashing incessantly. You turn your attention to the dark sky and before you know it, a huge lightning bolt strikes your ship. Initially, everything on the ship seems to have been unaffected. That is, until you have your meal and discover the spoon and knife attracted to your braces.

    You vividly remember the cutlery layout and seeing the lightning bolt strike the fork. But the fork isnt magnetized! Instead its the spoon and knife which are mangetized, with the handles having reversed polarities."

    Discuss why steel cutleries arranged in certain orientations are or are not magnetized by a huge electrical current. (4 marks)

    Question 3- Magnesia's Treasure
    You finally reach Magnesia, safe and sane at night. The surrounding is pitch dark and you are told that the entrance to the treasure lies Northward. Fortuitiously, you have in your pockets, a bare piece of copper wire, a flashlight, a dry cell and a compass. But the paint on the compass has faded and you can't tell the poles apart.

    Discuss without the Sun as a reference. How can you determine the poles of the compass? (4 Marks)

    2. Relevant equations

    3. The attempt at a solution

    I have solved question 3 and 1 roughly, but have trouble with question 2. Oh, and we have to use diagrams to solve as well.

    Question 1 is just that the ship will have a north seeking magnetic pole as well, as all magnets have two poles. Both poles would be influenced by the Earth's Magnetic field and the net result is that it does not move along the Earth's magnetic field. It is 3 marks though, i do not know if i have enough points there. I don't have diagrams for this one though.

    Question 3 i just used the plotting compass method, and Maxwells Corkscrew rule and the right hand rule to deduce that if the current goes down the wire, a clockwise magnetic field is formed. I would run the current down the wire and place the compass nearby to find out which end of the needle is north, from there finding out the rest. I have already got diagrams for this one.

    Question 2 I am not quite sure how to do. I think orientation basicalyl means which direction it is facing or something. I guess the spoon and knife have reversed polarities as they are facing different directions? Not much idea about the rest of it though. When you help me, please help me think of diagrams that I could use too.
  2. jcsd
  3. Jun 2, 2007 #2

    Chi Meson

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    Is this an exam? Are you allowed to seek any outside help for these questions?
    All I'll say for now is: consider the lightning bolt to be a straight current carrying wire.
  4. Jun 2, 2007 #3
    its not an exam. i can get some help.

    eh ok, so what you are saying is that the lightning bolt striking the fork, so the fork acts as the wire per se, generating a magnetic field around, such that the fork itself is not magnetized? and since the spoon and knife are on differnt sides, they will have different polarities?

    i thought of that but doesnt that require the fork to be standing up? wouldn't the cutlery be lying down?
  5. Jun 4, 2007 #4
    hmm any replies?
  6. Jun 6, 2007 #5
    can someone please help?
  7. Jun 8, 2007 #6
    o_O. This looks so familiar....:rofl:
  8. Jun 9, 2007 #7
    I normally would not give an explicit answer but I have seen you in desperate need, so there you go:

    1) because the magnetic poles do not exactly correspond with the geographic poles, they are tilted with a small angle, but in long distances, this creates a big deviation

    2)as Chi Meson suggested, treating the fork as a current carrying wire it produces magnetic fields with opposite directions on both sides, but the fork itself is not affected. using the right hand rule u can see that the directions of the magnetic fields produced on the spoon and the knife are opposite. that is why they have reversed polarities.

    3) using the cell and the copper wire create a magnetic field. determine the direction of this field using the + and - marks on the battery, then point the south pole of the magnet you created to the needle of the compass. because the needle itself is a magnet, its north end will be attracted. you now have the north end of the needle, hold the compass horizontally and see where that end points. (use the flaslight to be able to see in the dark)

    by the way, I enjoyed answering these questions, they are very good. where did you get them from?
  9. Jun 10, 2007 #8
    the giant ship wil surely have to move towards antartica, but i think two more forces are acting the ship at the same time, except forces of poles,these are the weight of ship, and resistance of water which reduces speed of ship.
    then to move further ship must have speed at least >or =viscocity coefficient of water. the lighjter the ship the larger the rate of ship towards pole, i think.
  10. Jun 16, 2007 #9
    i agree

    i totally laughed out loud at this question cos i got the very same one (word for word) in my file!
  11. Jun 16, 2007 #10
    hmm so noobski you have the questions as well? meaning you have the answers? are the stuff discussed in this thread correct?
  12. Jun 18, 2007 #11
    This is a teacher from your school. This is a graded assignment designed to test your knowledge. I request the participants' assistance in only dropping hints and not answers for enadiz. Thank you!
  13. Jun 25, 2007 #12


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    This thread's pretty amusing due to the number of new posters arriving. It occurs to me that the other posters have had the same idea as the OP and simply googled the question to see if it's been answered online before! Anyway, as someone mentioned, this forum is for homework help and, as such, complete solutions will not be given out to anyone asking a homework/exam type question.

    This sort of incident kinda points out how flawed the system of "take home exams" is in this day and age, but I guess that's a discussion for another time.
  14. Jun 25, 2007 #13
    well yeah i guess i should have made it a clearer point at the start that i required mostly hints and guide and not the answers. actually i mostly asked on this forum to doublecheck because i wanst very clear on the phrasing of the question, like question two. i completed the assignment before i really got any hints from here, and even then it didnt affect my answers.

    in any case i dont think one can call this an exam as we haven't even started learning this topic yet in school... so we definitely were meant to do our self research... but i do agree that the system is flawed as you say above
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