Every substance has some magnetic properties associated with it. The origin of these properties lies in the electrons. Each electron in an atom behaves like a tiny magnet. Its magnetic moment originates from two types of motions.

(i) Its orbital motion around the nucleus and

(ii) Its spin around its own axis.

Electron being a charged particle and undergoing these motions can be considered as a small loop of current which possesses a magnetic moment. Thus, each electron has a permanent spin and an orbital magnetic moment associated with it. Magnitude of this magnetic moment is very small and is measured in the unit called Bohr magneton, µB. It is equal to 9.27 × 10^–24 Am². On the basis of their magnetic properties, substances can be classified into five categories:

(i) Paramagnetic

(ii) Diamagnetic

(iii) Ferromagnetic

(iv) Antiferromagnetic and

(v) Ferrimagnetic.

Which of the following substances are weakly attracted by magnetic field?

Paramagnetic

The correct answer is option 2. Paramagnetic.

Let us delve into the explanations for each type of magnetic behavior:

1. Diamagnetic:

Diamagnetic substances are weakly repelled by magnetic fields. This repulsion occurs because when exposed to a magnetic field, diamagnetic materials generate small magnetic fields in the opposite direction to the applied field. Examples of diamagnetic materials include water, copper, and gold. Diamagnetism is a universal property of all materials and arises due to the motion of electrons within atoms.

2. Paramagnetic:

Paramagnetic substances are weakly attracted by magnetic fields. When placed in a magnetic field, paramagnetic materials develop a magnetic moment in the direction of the applied field, causing them to be weakly attracted to the field. This attraction arises due to the presence of unpaired electrons in the atoms, which align themselves with the external magnetic field. Examples of paramagnetic materials include oxygen, aluminum, and platinum.

3. Ferromagnetic:

Ferromagnetic substances are strongly attracted to magnetic fields and can retain magnetization even after the removal of the external field. In ferromagnetic materials, the magnetic moments of individual atoms align spontaneously in the same direction, resulting in a strong overall magnetization. Examples of ferromagnetic materials include iron, nickel, and cobalt.

4. Ferrimagnetic:

Ferrimagnetic substances are similar to ferromagnetic substances but exhibit a lower overall magnetization due to the presence of unequal numbers of magnetic moments aligned in opposite directions. Despite this, ferrimagnetic materials are still attracted to magnetic fields and can retain some magnetization after the external field is removed. Examples of ferrimagnetic materials include magnetite \((Fe_3O_4)\) and ferrites.

In summary, diamagnetic materials are weakly repelled, paramagnetic materials are weakly attracted, ferromagnetic materials are strongly attracted and retain magnetization, and ferrimagnetic materials are also attracted but have lower overall magnetization due to unequal alignment of magnetic moments.