The correct option is **C. Diamagnetic materials**. ### Detailed Explanation **1. Understanding Magnetic Susceptibility:** Magnetic susceptibility (χ) is a measure of how much a material will become magnetized in an applied magnetic field. It indicates the degree of magnetization of a material in response to an external magnetic field. - **Positive Magnetic Susceptibility (χ > 0):** Materials with positive susceptibility are attracted to magnetic fields. This includes ferromagnetic and paramagnetic materials. - **Negative Magnetic Susceptibility (χ < 0):** Materials with negative susceptibility are repelled by magnetic fields. This is characteristic of diamagnetic materials. **2. Characteristics of Diamagnetic Materials:** Diamagnetic materials have a very weak and negative susceptibility. When placed in a magnetic field, they develop a very weak magnetic field in the opposite direction, leading to a repulsive effect. Common examples of diamagnetic materials include bismuth, copper, and graphite. **3. Why Option C is Correct:** - **Repulsion from Magnetic Fields:** Diamagnetic materials are characterized by their ability to be repelled by magnetic fields due to their negative magnetic susceptibility. This means that when a diamagnetic material is placed in a magnetic field, it will experience a force that pushes it away from the source of the magnetic field. - **Behavior in Magnetic Fields:** When exposed to a magnetic field, diamagnetic materials do not retain any magnetization once the external field is removed, which is a key feature distinguishing them from ferromagnetic and paramagnetic materials. ### Explanation of Other Options **A. Ferromagnetic Materials:** - **Characteristics:** Ferromagnetic materials (like iron, cobalt, and nickel) have a high positive magnetic susceptibility. They are strongly attracted to magnetic fields and can retain magnetization even after the external field is removed. - **Why it's Wrong:** Ferromagnetic materials are not repelled by magnetic fields; they are attracted to them. **B. Paramagnetic Materials:** - **Characteristics:** Paramagnetic materials (such as aluminum and platinum) have a small positive magnetic susceptibility. They are weakly attracted to magnetic fields and do not retain magnetization once the external field is removed. - **Why it's Wrong:** Like ferromagnetic materials, paramagnetic materials are attracted to magnetic fields, not repelled. **D. Superparamagnetic Materials:** - **Characteristics:** Superparamagnetic materials are typically small ferromagnetic or ferrimagnetic particles that exhibit magnetic behavior similar to paramagnetic materials when they are small enough. They can be attracted to magnetic fields but do not retain magnetization. - **Why it's Wrong:** Superparamagnetic materials are also attracted to magnetic fields, not repelled. ### Summary of Key Points - **Diamagnetic materials** have a negative magnetic susceptibility and are repelled by magnetic fields. - They develop a weak magnetic field in the opposite direction when exposed to an external magnetic field. - Common examples include bismuth, copper, and graphite. - In contrast, ferromagnetic and paramagnetic materials are attracted to magnetic fields, while superparamagnetic materials behave similarly to paramagnetic materials under certain conditions. This understanding of magnetic susceptibility and the behavior of different materials in magnetic fields is crucial for grasping concepts in electromagnetism and material science.