Video Transcript
A bar magnet is hung from a
thread that is attached to a stand. The magnet can pivot
freely. What will happen if the north
pole of a second bar magnet is brought near to the north pole of the bar magnet
that is hanging from the thread? What will happen if the north
pole of the second bar magnet is brought near to the south pole of the bar
magnet that is hanging from the thread?
Okay, let’s say that this is
our bar magnet, this is the thread, and this is the stand that the thread is
hanging from. We’ll say that the blue side of
our bar magnet is the north pole and the pink side is the south pole. The first part of our question
asks this. It says, “What if we take a
second bar magnet and we bring the north pole of it near to the north pole of
the bar magnet hanging from the thread?”
To figure out what will happen
here, it’s helpful to remember that magnetic poles are a bit like electric
charge. When it comes to electric
charge, like charges repel one another and unlike charges attract. So we would say that positive
is drawn to negative but repelled from positive, and negative is drawn to
positive but repelled from negative. Well, the same sort of thing
happens with magnetic north and south Poles. Unlike poles, a north and a
south pole, attract one another, but like poles, for example, the north and
north pole we have here, repel one another.
For these bar magnets, because
the poles that are closest together are of a like type — they’re both north —
that means these magnets will repel one another. If we were to hold this second
bar magnet in place so that it couldn’t move, then the one that’s suspended by
the string would swing a bit backward. It’s pushed away from the other
bar magnet. We can write that out as a
sentence this way. We can say that the north pole
of the hanging bar magnet will be repelled by the north pole of the second
magnet.
In part two of this question,
we want to know what will happen if the north pole of the second bar magnet is
brought near to the south pole of the bar magnet that is hanging from the
thread. In this second scenario then,
here’s what we have. We have our second bar
magnet. But this time, the north pole
of this bar magnet is being brought near to the south pole of the suspended
magnet. In this case then, the two
poles that are closest to one another, the north and the south poles of these
two bar magnets, are of opposite types. Therefore, they’ll attract one
another. In this case, the suspended bar
magnet will be drawn towards the second bar magnet rather than repelled from
it.
Let’s write that out in answer
to this second part. Our answer is that the south
pole of the hanging bar magnet will be attracted to the north pole of the second
magnet. This is what will take place in
these two instances of bringing the second bar magnet close to the suspended bar
magnet.
