We use the term field when a force gets applied on an object by another
object without there being any physical contact between them. You have
observed this already in activity 1. Let us call this field which is responsible
for deflection of the compass needle as ‘magnetic field’.
• How was this field produced?
• Can we observe the field of a bar magnet?
Let us try.
Activity 2
Take a sheet of white paper and place it on the horizontal table. Place a
bar magnet in the middle of the sheet. Place a magnetic compass near the
magnet. It settles to a certain direction. Use a pencil and put dots on the
sheet on either side of the needle. Remove the compass. Draw a small line
segment connecting the two dots. Draw an arrow on it from South Pole of
the needle to North Pole of the needle. Repeat the same by placing the
compass needle at various positions on the paper. The compass needle
settles in different directions at different positions.
Why does this happen?
Remove the bar magnet and place the magnetic compass on the paper.
It comes to rest along the north-south direction. Now place the bar magnet
in its previous place.
• Is there any change in the direction of the needle of the magnetic
compass? Why?
The needle of the magnetic compass is affected by the bar magnet
without any physical contact. A force causes the needle to deflect and makes
it to come to rest in a certain direction.
• What is the nature of force that acts on the needle?
The force which acts on the needle from a distance is due to the
magnetic field of the bar magnet.
In activity 2, you have already seen that the orientation of needle is
different at different places on paper. This gives us an idea that the magnetic
field has direction and it varies from one point to another.
When you changes the place of the compass near the bar magnet you
can observe that its orientation changes from point to point. Now take the
needle to places far away on the sheet and observe the orientation of the compass needle in each case.