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Theory:

In the previous sections, we have learned about magnetic fields in detail. In this session, with the help of an activity, we will draw the field lines of a bar magnet.
  
Steps:
  • Set a sheet of white paper on a drawing board using some sticky material.
  • Locate a bar magnet in the centre of the paper.
2180507603_8a1dbef8d0_c.jpg
  • Spray some iron filings evenly around the bar magnet, as shown in the below figure. You may use a salt sprinkler for this purpose.
4580558571_371e7cfa0a_c.jpg
  • Now, tap the board mildly.
What do you observe?
  
Observation:
 
The iron filings organise themselves in a pattern, as shown in the below figure.
 
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Iron filings tracing the magnetic field of a bar magnet
  
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Magnetic field is shown by iron filings
  
Why do the iron filings arrange in such a pattern? What does this pattern illustrate?
The magnet exerts its impact in the area surrounding it. Therefore, the iron filings experience a force. The force thus exerted makes iron filings order in a pattern. The area surrounding a magnet (where the magnet's force can be recognised) has a magnetic field. The lines along which the iron filings arrange themselves denote magnetic field lines.
Are there any different ways of obtaining magnetic field lines around a bar magnet?

Yes. You can draw yourself the field lines of a bar magnet.
 
In the upcoming sections, we will do an activity to draw the field lines of a bar magnet by ourselves.
Reference:
https://www.flickr.com/photos/daynoir/2180507603
https://www.flickr.com/photos/oskay/4580558571/in/photostream/
https://www.flickr.com/photos/daynoir/2181293650/
https://www.flickr.com/photos/daynoir/2180506627/in/photostream/