Understanding Paramagnetic Substances

Paramagnetic substances are a class of materials that exhibit a specific behavior when exposed to an external magnetic field. Their magnetic properties are distinct from diamagnetic and ferromagnetic materials.

Behavior of Paramagnetic Materials in a Magnetic Field

When a paramagnetic substance is placed in an external magnetic field, the individual magnetic dipoles within the material (which are randomly oriented in the absence of a field) tend to align partially with the direction of the external field. This alignment causes the material to become weakly magnetized in the same direction as the applied field.

Because of this weak magnetization aligned with the field, paramagnetic substances are:

• Weakly attracted to regions of strong magnetic field.
• Drawn into a magnetic field.

The attraction is weak compared to ferromagnetic materials like iron.

Analyzing the Options

Let's examine each provided option in the context of the properties of paramagnetic substances:

• Option 1: Produced by heating iron above the curie point

  This statement is partially related but describes a process involving a different class of magnetic material. Iron is typically ferromagnetic. When ferromagnetic materials like iron are heated above their Curie temperature, they lose their strong ferromagnetic properties and become paramagnetic. So, while heating iron above its Curie point results in a paramagnetic state, this option describes the *transition* for iron, not the inherent property of all paramagnetic substances.

• Option 2: Weakly repelled by a magnet

  This describes the behavior of diamagnetic substances. Diamagnetic materials are weakly magnetized in the opposite direction to an external magnetic field, causing them to be weakly repelled by a magnet. This is the opposite behavior of paramagnetic substances.

• Option 3: Weakly attracted by a magnet

  This statement accurately describes the characteristic behavior of paramagnetic substances. As explained earlier, paramagnetic materials align weakly with the external magnetic field and are thus weakly attracted to it.

• Option 4: The same as that of dia magnetic substances

  This is incorrect. Paramagnetic and diamagnetic substances have opposite magnetic behaviors in an external field. Paramagnetic substances are weakly attracted, while diamagnetic substances are weakly repelled.

Conclusion on Paramagnetic Properties

Based on the analysis of the magnetic behavior of different materials, paramagnetic substances are characterized by being weakly attracted by a magnet when placed in an external magnetic field. This is due to the partial alignment of their atomic magnetic dipoles with the applied field.

Revision Table: Types of Magnetic Materials

Additional Information on Magnetism

The magnetic properties of materials arise from the magnetic moments of the electrons within their atoms. These moments are associated with electron spin and orbital motion. In different materials, these atomic magnetic moments interact in different ways:

• In paramagnetic materials, the atoms have permanent magnetic moments, but they are randomly oriented due to thermal motion. An external field provides a weak aligning force.
• In diamagnetic materials, atoms generally do not have permanent magnetic moments. An external magnetic field induces a temporary magnetic moment in the opposite direction, according to Lenz's Law.
• In ferromagnetic materials, there are strong interactions between atomic magnetic moments, causing them to align parallel to each other within regions called domains, even without an external field. This leads to strong magnetization and attraction.

The degree of magnetization in a material is described by its magnetic susceptibility ($\chi_m$). For paramagnetic materials, $\chi_m$ is small and positive. For diamagnetic materials, $\chi_m$ is small and negative. For ferromagnetic materials, $\chi_m$ is large and positive.