Diamagnetism

Definition

Diamagnetism is a fundamental property of all materials, where the application of an external magnetic field induces a weak magnetic field within the material that opposes the external field. This phenomenon arises from the motion of electrons within the atoms of the material, which creates a small magnetic moment that aligns against the applied field.

5 Must Know Facts For Your Next Test

1. Diamagnetism is a universal property of all materials, but it is typically very weak and overshadowed by other magnetic effects in most substances.
2. Diamagnetic materials, such as copper, gold, and water, are repelled by magnetic fields and have a negative magnetic susceptibility.
3. The diamagnetic effect is caused by the orbital motion of electrons within atoms, which creates a small magnetic moment that opposes the applied magnetic field.
4. Superconductors are perfect diamagnets, completely expelling magnetic fields from their interior due to the formation of persistent currents on their surface.
5. Diamagnetism can be used to levitate small objects, such as a frog or a piece of graphite, when placed in a strong enough magnetic field.

Review Questions

• Explain the mechanism behind diamagnetism and how it arises from the motion of electrons within atoms.
  • Diamagnetism is a fundamental property of all materials, where the application of an external magnetic field induces a weak magnetic field within the material that opposes the external field. This phenomenon is caused by the orbital motion of electrons within the atoms of the material. When a magnetic field is applied, the electrons' orbits are slightly altered, generating a small magnetic moment that aligns in the opposite direction to the applied field, in accordance with Lenz's law. This induced magnetic field within the material opposes the original field, resulting in the diamagnetic effect.
• Describe the relationship between diamagnetism and magnetic susceptibility, and explain how diamagnetic materials are characterized.
  • Diamagnetic materials have a negative magnetic susceptibility, meaning they are repelled by magnetic fields. The degree of diamagnetism in a material is quantified by its magnetic susceptibility, which is a measure of the material's ability to be magnetized in an external magnetic field. Diamagnetic materials, such as copper, gold, and water, have a very small and negative magnetic susceptibility, typically on the order of -10^-5 to -10^-6. This weak diamagnetic response is a universal property of all materials, but it is often overshadowed by stronger magnetic effects in many substances.
• Explain how diamagnetism can be used to levitate objects and discuss the potential applications of this phenomenon.
  • Diamagnetism can be used to levitate small objects, such as a frog or a piece of graphite, when placed in a strong enough magnetic field. This is because the induced diamagnetic effect in the object creates a magnetic field that opposes the applied field, resulting in a net force that counteracts the gravitational force on the object, causing it to levitate. The ability to levitate objects using diamagnetism has potential applications in areas such as frictionless bearings, magnetic levitation trains, and the study of biological systems in a near-weightless environment. Additionally, the perfect diamagnetism exhibited by superconductors, which completely expel magnetic fields from their interior, has important applications in technologies like MRI machines and high-speed maglev trains.

Related terms

Magnetic Susceptibility: A measure of the degree to which a material can be magnetized in an external magnetic field, with diamagnetic materials having a negative magnetic susceptibility.

Eddy Currents: The circular electric currents that are induced within a conductive material when it is exposed to a changing magnetic field, which can create a magnetic field opposing the original field.

Lenz's Law: The principle that the direction of the induced current in a conductor is such that it opposes the change in the magnetic field that caused it, in accordance with the law of conservation of energy.