Page 151 - SCERT Kerala State Syllabus 8th Standard Basic Science Textbooks English Medium Part 1_Neat

connecting these points in the north south direction. Keeping this
line in the north south direction, place a bar magnet in the middle
so that its north pole points towards the north of the earth. Trace
the boundary NS of the bar magnet on the paper (Fig.11.7). Bring
a magnetic compass near the north pole.
Which end of the magnetic needle does the north pole of the
magnet attract? Note down.

Mark a dot on the paper near the free end of the north pole of the
magnetic needle. Now change the position of the compass such
that its centre falls on the dot. Mark the position of the north pole
of the compass needle. Repeat the process. Didn’t you get a large
number of points on the paper? Draw a line joining these dots.
This is an imaginary line indicating the influence of magnetic force
and its direction. Such a line is the magnetic line of force.
Repeat the process a number of times placing the compass at
different positions near the north pole of the magnet and draw
more magnetic lines of force extending upto the south pole. Do
all the lines of force reach the south pole of the magnet? Haven’t
you observed that the direction of magnetic lines of force is from
the north pole to the south pole outside the magnet? It is
considered to be from the south pole to the north inside a magnet.
Is the distribution of magnetic lines of force the same everywhere?

In the figure you have drawn, where do you see the magnetic
lines of force close to one another? Write it down.
Magnetic Flux Density

Are magnetic lines of force present in all dimensions around a
magnet? Let’s do an experiment.

Using a thread suspend a bar magnet as shown in
Fig. 11.8. Now bring the needle of a magnetic compass to
N
different positions around its north and south poles. What
do you observe?
Isn't the influence of the magnetic force experienced in
all positions? We understand the presence of magnetic
S
lines of force from this. What is your inference? Write it
down.
Magnetic lines of force are experienced in all dimensions
around a magnet.
Fig. 11.8
150 Basic Science VIII