Question 12 Marks
Draw a clearly labelled diagram, to show how a steel bar is magnetised by a divided touch method. A written description is not required.
Questions
[2 Mark Question Answer]
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Question 22 Marks
Draw the magnetic flux pattern near a bar magnet placed with its axis in the magnetic meridian and the south pole pointing towards geographic north.
Answer
View full question & answer→Geoaraphic north or Magnetic south
Question 32 Marks
The figure shows a freely suspended magnet in rest position. Copy the diagram and on it show :
(a) Angle of declination
(b) Angle in dip
(a) Angle of declination
(b) Angle in dip
Question 42 Marks
Explain, why steel is used in preference to soft iron for making permanent magnets while soft iron is used in preference to steel for making electromagnets.
Answer
View full question & answer→Steel is used in preference to soft iron for making permanent magnets because steel acts as a magnet, even on the removal of inducing magnet and also steel has a very high retention. Soft iron is used in preference to steel for making permanent magnets because soft iron behave like magnet as long as there is an inducing magnet and alsosoft iron has a very poor magnetic retention.
Question 52 Marks
There are two knitting needles. One of them is magnetised. How will you find out which one is magnetised, if no other magnet is available?
Answer
View full question & answer→When an iron bar is magnetised, it slightly increases in length due to setting of molecular magnets along straight chains. So, on precisely measuring the length of knitting needle, the knitting needle which is slightly longer in length than other is magnetised.
Question 62 Marks
Repulsion is a surer test of magnetic condition of a body than attraction. Explain.
Answer
View full question & answer→Repulsion is the surest test of magnetism because the attraction can be caused between two unlike poles of the two magnets or between the magnet and magnetic substance such as iron, nickel etc. But repulsion is caused when two similar poles approach each other.
Question 72 Marks
Why do lines of magnetic force never cross? Why do they never pass through a neutral point?
Answer
View full question & answer→No two lines of magnetic force cross each other because in that case there would be two directions of resultant magnetic force at a given point, which is not possible. Magnetic lines of force never pass through neutral point because at neutral point magnetic field due to bar magnet is neutralised by earth's magnetic field.