**Correct Option: B. Copper** ### Explanation of the Correct Answer **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. - **Diamagnetic materials** have a negative magnetic susceptibility (χ < 0). This means they are weakly repelled by a magnetic field. When placed in a magnetic field, they create an induced magnetic field in the opposite direction, leading to a net repulsion. - **Paramagnetic materials** have a positive magnetic susceptibility (χ > 0) and are weakly attracted to magnetic fields. - **Ferromagnetic materials** (like iron, nickel, and cobalt) have a very high positive susceptibility and can become permanently magnetized. **2. Identifying the Materials:** Now, let's analyze the options provided: - **A. Iron:** Iron is a ferromagnetic material with a high positive susceptibility. It is strongly attracted to magnetic fields and can retain magnetization. - **B. Copper:** Copper is a diamagnetic material. It has a negative magnetic susceptibility, meaning it is weakly repelled by magnetic fields. This property arises because the electrons in copper rearrange slightly in response to an external magnetic field, creating a small opposing magnetic field. - **C. Nickel:** Nickel is also a ferromagnetic material, similar to iron, and has a high positive susceptibility. It is attracted to magnetic fields and can be magnetized. - **D. Cobalt:** Cobalt is another ferromagnetic material, exhibiting strong magnetic properties and a high positive susceptibility. ### Why Other Options Are Incorrect - **Iron (A):** Incorrect because it is ferromagnetic, not diamagnetic. It has a high positive susceptibility and is strongly attracted to magnetic fields. - **Nickel (C):** Incorrect for the same reason as iron. Nickel is ferromagnetic and has a high positive susceptibility. - **Cobalt (D):** Incorrect as well, since cobalt is also ferromagnetic and exhibits strong attraction to magnetic fields. ### Summary of Key Concepts - **Diamagnetic Materials:** Characterized by negative magnetic susceptibility (χ < 0). They are weakly repelled by magnetic fields. Examples include copper, bismuth, and graphite. - **Ferromagnetic Materials:** Characterized by high positive magnetic susceptibility (χ > 0). They are strongly attracted to magnetic fields and can retain magnetization. Examples include iron, nickel, and cobalt. ### Common Pitfalls - Confusing diamagnetic materials with ferromagnetic materials. Remember that diamagnetic materials are weakly repelled, while ferromagnetic materials are strongly attracted. - Not recognizing that some materials can exhibit different magnetic properties under different conditions (e.g., temperature changes can affect magnetic behavior). ### Revision Summary - **Diamagnetic materials** have negative magnetic susceptibility and are weakly repelled by magnetic fields (e.g., copper). - **Ferromagnetic materials** have high positive susceptibility and are strongly attracted to magnetic fields (e.g., iron, nickel, cobalt). - Always check the magnetic properties of materials when classifying them as diamagnetic or ferromagnetic. - Remember that the arrangement of electrons in a material plays a crucial role in its magnetic properties.