The correct option for the question is **B. Paramagnetic materials**. Let's break down the reasoning behind this answer and clarify why the other options are not correct. ### Explanation of the Correct Answer (B: Paramagnetic materials) 1. **Definition of Paramagnetic Materials**: - Paramagnetic materials are substances that have unpaired electrons, which allow them to be attracted to an external magnetic field. When an external magnetic field is applied, these materials become magnetized in the direction of the field. 2. **High Permeability**: - Permeability is a measure of how easily a material can become magnetized or how well it can conduct magnetic lines of force. Paramagnetic materials have high permeability, meaning they can easily be magnetized when exposed to a magnetic field. 3. **Temporary Magnetization**: - A key characteristic of paramagnetic materials is that they do not retain significant magnetization once the external magnetic field is removed. This means that their magnetization is temporary and directly related to the presence of the external field. When the field is taken away, the material loses its magnetization almost completely. ### Why the Other Options Are Incorrect **A. Ferromagnetic materials**: - **Characteristics**: Ferromagnetic materials (like iron, cobalt, and nickel) have a strong tendency to become magnetized and can retain significant magnetization even after the external magnetic field is removed. This property is known as hysteresis. - **Conclusion**: Since ferromagnetic materials retain magnetization, they do not fit the criteria of the question. **C. Diamagnetic materials**: - **Characteristics**: Diamagnetic materials (like copper and bismuth) are characterized by their weak repulsion to magnetic fields. They do not have unpaired electrons and exhibit a very weak negative susceptibility to magnetic fields. - **Conclusion**: Diamagnetic materials do not become magnetized in the presence of an external magnetic field, which makes them unsuitable for the question. **D. Superparamagnetic materials**: - **Characteristics**: Superparamagnetic materials are typically small ferromagnetic or ferrimagnetic nanoparticles that can become magnetized in the presence of a magnetic field but do not retain magnetization once the field is removed. However, they are still fundamentally different from paramagnetic materials because they can exhibit strong magnetic behavior under certain conditions. - **Conclusion**: While superparamagnetic materials do not retain magnetization, they are not characterized by high permeability in the same way that paramagnetic materials are. ### Summary of Key Points - **Paramagnetic materials** have unpaired electrons, allowing them to be attracted to magnetic fields and exhibit high permeability. - They **do not retain significant magnetization** once the external magnetic field is removed, making them distinct from ferromagnetic materials. - **Ferromagnetic materials** retain magnetization, while **diamagnetic materials** are weakly repelled by magnetic fields and do not become magnetized. - **Superparamagnetic materials** can exhibit temporary magnetization but are fundamentally different from paramagnetic materials. ### Revision Summary - **Paramagnetic materials**: High permeability, temporary magnetization, do not retain magnetization after the field is removed. - **Ferromagnetic materials**: Strong magnetization, retain magnetization after the field is removed. - **Diamagnetic materials**: Weakly repelled by magnetic fields, do not become magnetized. - **Superparamagnetic materials**: Exhibit temporary magnetization but differ from paramagnetic materials in behavior and characteristics.