Question

differentiate between single touch method and double touch method

Answer 1

Single Touch Method

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.


Double Touch Method
The double-touch method is similar to the single-touch method, except that two bar magnets of equal strengths are used instead of one.
To magnetise a steel strip AB, Place the opposite ends of the two magnets at the centre, C, of this strip, as shown in the above figure.
Drag the poles of these two magnets towards the ends of the strip such that the magnets rub the strip firmly all the way.
The south pole is dragged towards end A and the north pole is dragged towards end B.
Repeating this procedure a number of times, the steel strip gets magnetised and the end A becomes the north pole and end B becomes the south pole.
To make a stronger magnet, the two ends of the steel strip are rested on the two poles of two other magnets. The pole on which the strip rests should match the pole that strokes that end.

Thus, A should rest on the south pole and B on the north pole.