Page 154 - SCERT Kerala State Syllabus 8th Standard Basic Science Textbooks English Medium Part 1_Neat

two pins together close to the north pole of the magnet. How
do the free ends remain? Mark the polarity of the free ends in
Fig.11.12 (b).
Now bring the pin near one of the poles of the magnet as shown
in Figure 11.12 (c).

Haven't we learnt that the pin changes into a magnet? Examine
using a magnetic needle, the magnetic pole formed at the
farthest end of the pin. We find that the polarity developed at
the farthest end is the same as that of the tip of the magnet, with
which the pin is in contact. What are the inferences you arrive
at from the experiments? Write it down.
Whether under contact or without contact, the polarity of the
magnet produced by induction will be like polarity at the farther
end and unlike polarity at the nearer end.

Magnetic Induction in Soft Iron and Steel

Place a soft iron piece on any one pole of a bar
magnet as shown in Fig.11.13. Thrust the free end
of the iron piece in a heap of pins and take it out.
Count the number of pins that get attracted?
Holding the soft iron piece, remove the bar
magnet. What do you observe? Why did all the
pins fall down?
Repeat the experiment using a piece of steel of
the same size instead of the soft iron piece. Count
the number of pins that get stuck onto the piece
of steel and write it down.
What do you observe on removing the bar
magnet? Do all pins fall down? What is the reason?

Here both soft iron and steel get magnetised when
placed in a magnetic field.
Which of these has greater susceptibility?
(Soft iron/Steel)

Which of these has greater retentivity?
(Soft iron/Steel)
Fig. 11.3

Basic Science VIII 153