Question

what are the precautions to be taken while magnetising a sewing needle with single touch method

Answer 1

In the single-touch method, an iron bar is rubbed with a magnet repeatedly. To magnetise an iron bar AB using a bar magnet.

Place one of the poles of a bar magnet, say the north pole, over one end of the iron bar, say end A.

Without lifting the bar magnet, move it along the length of the iron bar till you reach the other end, B, of the bar.
On reaching end B of the iron bar, lift the bar magnet, bring the same north pole to point A of the iron bar, and then rub move the magnet from point A to point B again.
The process needs to be repeated about 30 to 40 times.

This process is called magnetisation of the iron bar by the single-touch method. The end A becomes the north pole and B the south pole, which can be checked by means of a magnetic compass or a bar magnet.

Precaution to be taken:
1) Use only one side of magnet to rub on the surface of iron (you can use either S pole or N pole).
2)Do not go to and fro in the rubbing, you need to rub in one direction only.
3) To get more powerful magnet repeat this process for 50 times.