Video Transcript
The diagram below shows a bar
magnet and a copper ring. Some of the field lines of the
magnetic field produced by the bar magnet are shown. Fill in the blank. If the copper ring is moved away
from the bar magnet, the number of field lines shown that will pass through it will
(A) increase, (B) decrease, or (C) stay the same.
So in this image, a bar magnet is
at at close distance to a copper ring. We need to decide how moving the
ring away from the magnet will affect the number of field lines that will pass
through the ring. We can answer this question by
simply counting the number of field lines in the diagram that pass through the
ring. Initially, we can count that four
of the field lines shown will pass through the ring.
Now let’s imagine moving the ring
away from the magnet, to here, for example. Now only two field lines pass
through the ring. If we move the ring even further
away, to here, only one field line passes through the ring. So the further the ring is from the
magnet, the fewer the field lines that pass through the ring. This tells us that the answer must
be option (B). If the copper ring is moved away
from the bar magnet, the number of field lines shown that will pass through it will
decrease.
