Three specimens of magnetic material were tested using the apparatus shown in the diagram.
When the switch is closed, the specimen picks up some of the iron nails but when the switch is opened, many or most of the nails fall off. The number of nails picked up and left on were found for three specimens. The table shows the results.
Specimen Number of nails picked up Number of nails left on
X 35 4
Y 20 10
Z 40 3

Which material among the following is suitable for making use in compasses?

Question

Q.

Three specimens of magnetic material were tested using the apparatus shown in the diagram.
When the switch is closed, the specimen picks up some of the iron nails but when the switch is opened, many or most of the nails fall off. The number of nails picked up and left on were found for three specimens. The table shows the results.

Specimen	Number of nails picked up	Number of nails left on
X	35	4
Y	20	10
Z	40	3

Which material is the best electromagnet among the three?

Answer 1

Number of nails picked up shows how easily the material can be magnetised. The number of nails left on the material is a proof of the retained magnetism when current is removed. Therefore, material Z is the best electromagnetise ( attracts 40 nails) and looses its magnetism when the switch opened (left only 3 nails) . Material X is also suitable to use as electromagnet, but not as good as Z.