Magnetic Materials

Magnetic Materials

Activity 5

Spread some iron pins, stapler pins, iron nails, small pieces of paper, a scale, an eraser and a plastic cloth hanger on a wooden table. Place a magnet nearby these materials. What do you observe? List out which of these things are attracted by the magnet? Which objects are not attracted? Tabulate your observations.

Answer:

Aim : To understand the behaviour of magnetic and non-magnetic materials.

Materials attracted by magnet

Iron pins

Stapler pins

Iron nails

Materials not attracted by magnet

Scale

Eraser

Small pieces of paper

Plastic cloth hanger

Materials which are attracted by magnets are called magnetic materials and those materials which are not attracted by magnets are called non-magnetic materials. There are a number of materials that can be attracted by magnets. These can be magnetised to create permanent magnets. Magnetic materials can be categorised as magnetically hard or magnetically soft materials. Magnetically soft materials are easily magnetised. Magnetically hard materials also can be magnetised but they require a strong magnetic field to be magnetised. It is because materials have different atomic structure and they behave differently when they are placed in a magnetic field. Based on their behaviour in a magnetic field they can be classified as below.

* Diamagnetic materials

* Paramagnetic materials

* Ferromagnetic materials

1. Diamagnetic materials

Diamagnetic materials have the following characteristics.

* When suspended in an external uniform magnetic field they will align themselves perpendicular to the direction of the magnetic field

* They have a tendency to move away from the stronger part to the weaker part when suspended in a non-uniform magnetic field.

* They get magnetised in a direction opposite to the magnetic field.

* Examples for diamagnetic substances are bismuth, copper, mercury, gold, water, alcohol, air and hydrogen.

* Magnetic character of these substances is not affected by the external temperature.

2. Paramagnetic materials

The following are the characteristics of paramagnetic materials.

* When suspended in an external uniform magnetic field they will align themselves parallel to the direction of the magnetic field.

* They have a tendency to move from the weaker part to the stronger part when  suspended in a non-uniform magnetic field.

* They get magnetised in the direction of the field.

* Examples for paramagnetic substances are aluminium, platinum, chromium, oxygen, manganese, solutions of salts of nickel and iron.

* Magnetic character of these substances is affected by the external temperature.

3. Ferromagnetic materials

The characteristics of ferromagnetic materials are given below.

* When suspended in an external uniform magnetic field they will align themselves parallel to the direction of the magnetic field.

* It has a tendency to move quickly from the weaker part to the stronger part when suspended in a non-uniform magnetic field.

* They get strongly magnetised in the direction of the field.

* Examples for ferromagnetic substances are iron, cobalt, nickel, steel and their alloys.

* Magnetic character of these substances is affected by the external temperature. When they are heated they become para magnetic.

More to know

The temperature, at which the ferromagnetic material becomes paramagnetic is called the curie temperature.