Fun With Magnets

As we know unlike poles attract each other & like poles repel each other. So, in A, two cars are facing each other such that unlike poles are closer to each other. Therefore car 1 & car 2 will come closer. But in B, like poles are facing each other and will therefore repel that is move away from each other.

With time magnets lose their magnetic properties. So in order to retain their magnetic strength, the pair of magnets is kept with unlike poles in the same direction with a wooden block between them and metal plates made up of soft iron are placed across the poles as shown in figure (b). This arrangement preserves the magnetic strength of magnets by completing the magnetic circuit.

As we can see from the given figure, A attracts more iron fillings followed by magnet B. Magnet C hardly attracts any iron filings. From the level of attraction of iron fillings we can definitely say that strength of A is more than B & strength of B is more than C.

It will be easy for us to identify the north pole of a magnet (1) with the help of another magnet (2) whose North Pole & South Pole are marked as if we bring North pole of the magnet (2) to the poles of magnet (1), then the pole which will repel is the North pole of magnet (1).

Poles have the maximum magnetic strength of equal intensity. Therefore, the amount of iron fillings attracted to both the boles will be almost equal.

(i) When a bar magnet is broken; each of the broken part will have two pole/poles.
When the magnet is broken then each part of the broken magnet will develop its own North & South Pole.

(ii) In a bar magnet, magnetic attraction is more/greater near its ends.
North & South Pole have magnetic strength greater than the rest part of the magnet.

Magnet attracts only those metals which have magnetic properties in them like iron, nickel, cobalt and so on. Here the pins are made up of stainless steel which is non-magnetic in nature. Therefore, the pins will not be attracted towards the magnet.

It can be tested whether tea dust is adulterated with iron powder or not if we use a magnet. We move the magnet over the tea dust then if it’s adulterated, iron powder will be attracted to the magnet and if it’s not then magnet will come out clean.

(i) The two ends of the magnet will have more iron fillings sticking to it as they have the maximum magnetic strength.

(ii) These regions are called North Pole & South Pole

(a) In the given figure we can see that the iron bar in figure (a) attracts the maximum iron fillings. There (a) is the strongest magnet.

(b) Iron bar (b) is not a magnet as it does not attract any iron fillings.

To determine which pole of the magnet is facing the front of the car, use another magnet whose North & South pole is marked. Now bring any pole, say North Pole of the magnet towards the magnet which is facing the front of the car. If they repel, then it is North Pole which is facing the front and if they get attracted, then it’s South Pole which is facing the front of the car.

The two ways are:

● Put both the metal bars in the heap of iron fillings and bring them out. The one which attracts the iron fillings will be the magnet.

● Bring another magnet towards both the metal bars. The metal bar which attracts/repel the magnet is itself a magnet.

We can find the other magnet with the help of magnet in which North & South poles are marked. Bring the marked magnet closer to the other two iron bars. Both the bars will be attracted towards the magnet as they are both made up of iron. So to test magnet, repulsion of like poles are to be used. Bring the poles of iron bars one by one towards the north pole of the magnet. The iron bar will be attracted but the actual magnet can get attracted or get repelled. Now change the poles of the iron bars. The magnet will be attracted/repelled but the iron will only be attracted.

The steps involved in magnetizing an iron strip with the help of magnet are:

● Place the iron strip which is to be magnetized on a wooden table.

● Take a bar magnet in such a manner that one end of the magnet is held in the hands and the other end is on one edge of the strip.

● Move the magnet, without lifting, along the length of the strip till the other edge is reached.

● Repeat the above steps several times.

● Bring the iron fillings and spread it on the strip. If it gets attracted the the strip gets magnetized and if it’s not then repeat the steps few more times.

As magnetic compass is made up of magnet only so it will follow the magnetic properties. When North Pole of the magnet is brought near the compass, then North Pole of the compass will deflect/repel and South Pole of the compass will be attracted to the magnet. If we bring South Pole of the magnet towards the compass then North Pole of the compass will be attracted & South Pole will be deflected.

Steps to make a magnetic compass:

● Place the needle on a wooden table.

● Rub the magnet across its length without lifting it.

● Once the end point of needle is reached, lift the magnet and again rub it in the same direction.

● Remember not to change the direction and repeat the steps a dozen times.

● Now place the needle on the cork in a vessel containing water.

● The needle will move and align itself in the North-South direction.

The iron bar can be used as a magnet as it has induced some magnetic properties from the bar magnet present there. The pin cannot be used as a magnet as it has very small area and as it is not in direct contact with the magnet, the magnetic strength is very less. Therefore it cannot induce magnetic properties.

Steps to show that they have/have not induced magnetic properties are:

● Place the iron bar & pin on the table just after it is being separated from the magnet.

● Now use iron fillings and spread it over the iron bar and the pin.

● We will infer that iron bar attracts some iron fillings but not the pin.

A magnet can be considered as a combination of smaller magnetic dipoles.

When we break a magnet into two halves lengthwise these dipoles get separated and act as individual magnets.

So, yes the two pieces will act as individual magnets.

The poles of new magnets can be detected by using a compass or by test of repulsion between newly formed magnets.

So new poles are marked as:

A U magnet is stored in a wooden box with a soft iron placed at the edge. A bar magnet is kept in pairs with opposite poles facing the same direction and separated by a wooden block. The two edges of the magnet are joined by soft iron bar.