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GR0177 #7
Problem
 GREPhysics.NET Official Solution Alternate Solutions
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Electromagnetism$\Rightarrow$}Field Lines

Since one has same polarity magnet ends at the same side, one can immediately cancel out choices (A) and (D). They would repel each other, and thus the field-lines would not be pointing towards each other. Since there are no such things as magnetic monopoles, one cannot have choice (C), as that would imply a non-zero divergence in the magnetic field. Choice (D) would work if there were a current through the magnets, but there's not. Choice (B) remains. It makes sense since the magnetic charges should repel each other, and thus the field lines should point away showing the repulsion.

Alternate Solutions
 natec2013-09-17 12:29:20 Have any of you heard of a Dirac monopole? Its essentially a half infinite solenoid/bar magnet. In this case the end of the magnet near you (the end NOT off at infinity) will look like a magnetic monopole since it is a source of B field! Too me, these two bar magnets looked like dirac monopoles since the south pole was 'far away' from the paper, which would create a B field analogous to an E field for electric monopoles (AKA point charges) which would give you B.Reply to this comment jmason862009-07-13 20:07:12 Or if you've ever done this experiment in elementary school... just remember what the iron fillings did. Reply to this comment Ning Bao2008-02-01 05:39:05 There must be no field in right between the two magnets because a particle put there would be in an unstable equilibrium -> B or E. E is wrong because you don't expect the fields to only be depended on distance away from a mingle pole.Reply to this comment
natec
2013-09-17 12:29:20
Have any of you heard of a Dirac monopole? Its essentially a half infinite solenoid/bar magnet. In this case the end of the magnet near you (the end NOT off at infinity) will look like a magnetic monopole since it is a source of B field! Too me, these two bar magnets looked like dirac monopoles since the south pole was 'far away' from the paper, which would create a B field analogous to an E field for electric monopoles (AKA point charges) which would give you B.
gravity
2010-11-09 21:47:10
lol. boobs.
 yummyhat2017-10-25 04:01:22 Kappa
jmason86
2009-07-13 20:07:12
Or if you've ever done this experiment in elementary school... just remember what the iron fillings did.
Ning Bao
2008-02-01 05:39:05
There must be no field in right between the two magnets because a particle put there would be in an unstable equilibrium -> B or E. E is wrong because you don't expect the fields to only be depended on distance away from a mingle pole.
OrbitGirl
2007-10-03 11:00:34
Choice (D) would work if there were a current through the magnets...

I think you meant (E).
cailh
2006-10-28 06:34:51

LaTeX syntax supported through dollar sign wrappers $, ex.,$\alpha^2_0$produces $\alpha^2_0$. type this... to get...$\int_0^\infty$$\int_0^\infty$$\partial$$\partial$$\Rightarrow$$\Rightarrow$$\ddot{x},\dot{x}$$\ddot{x},\dot{x}$$\sqrt{z}$$\sqrt{z}$$\langle my \rangle$$\langle my \rangle$$\left( abacadabra \right)_{me}$$\left( abacadabra \right)_{me}$$\vec{E}$$\vec{E}$$\frac{a}{b}\$ $\frac{a}{b}$