Unit: Magnetism
Year: 1993 Question#: 34
Question: The diagram below shows the magnetic field that results when a piece of iron is placed between unlike magnetic poles.
At which point is the magnetic field strength greatest?
(1 ) A
(2 ) B
(3 ) C
(4 ) D
What is this question really asking?
Explanation by: Steve W.
[ Return to question menu ]
Answer 1
A
INCORRECT
Point A is where the field strength is the weakest. You do not want to identify where the lines of flux are farthest apart.
return to top Answer 2
B
INCORRECT
Point B is ordinarily where the magnetic field is the strongest (closest to the poles of the magnet). Unfortunately answer D would be equally acceptable for the same reason. As a result of the iron being more permeable to the magnetic field the iron actually allows the field to concentrate, making the lines closer together than near the poles.
return to top Answer 3
C
CORRECT
Point C is the the location where the magnetic field lines are closest together. They are "focused" in the iron because the iron is more permeable to the magnetic field than the air is. As a result the field concentrates in the iron more than in the surrounding air. Field strength is indicated by where the field lines (lines of flux) are closest together.
return to top Answer 4
D
INCORRECT
Point D is ordinarily where the magnetic field is the strongest (closest to the poles of the magnet). Unfortunately answer B would be equally acceptable for the same reason. As a result of the iron being more permeable to the magnetic field the iron actually allows the field to concentrate, making the lines closer together than near the poles.
return to top What's this question really asking?
The question is asking you if you can identify where the magnetic field strength is the highest. The field strength is the greatest where the lines of magnetic flux are closest together. return to top
