Science
A student fixes a sheet of white paper on a drawing board using some adhesive materials. She places a bar magnet in the centre of it and sprinkles some iron filings uniformly around the bar magnet using a salt-sprinkler. On tapping the board gently, she observes that the iron filings have arranged themselves in a particular pattern.
(a) Draw a diagram to show this pattern of iron filings.
(b) Draw the magnetic field lines of a bar magnet showing the poles of the bar magnet as well as the direction of the magnetic field lines.
(c) (i) How is the direction of magnetic field at a point determined using the field lines ? Why do two magnetic field lines not cross each other ?
OR
(ii) How are the magnetic field lines of a bar magnet drawn using a small compass needle ? Draw one magnetic field line each on both sides of the magnet.
Electro-Magnetism
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Answer
(a) Below diagram shows the pattern of iron filings:
(b) The magnetic field lines of a bar magnet and its poles are shown below:
(c) (i) The direction of the magnetic field lines at a place can be determined by using a compass needle.
Two magnetic field lines never intersect each other. If they would intersect, this would mean that there are two directions of the field at the specific point which is not possible.
OR
(ii) Magnetic field lines can be mapped out using a small compass.
We will mark the position of two ends of the needle of the compass.
Now we will move the needle to a new position such that its south pole occupies the position previously occupied by its north pole.
In this way, we will proceed step by step till we reach the south pole of the magnet as shown in Fig.
Now we will join the points marked on the paper by a smooth curve. This curve represents a field line.
We will repeat the above procedure, and get the magnetic field lines around the magnet.
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