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Related Concept Videos

Diamagnetism01:26

Diamagnetism

Materials consisting of paired electrons have zero net magnetic moments. However, when these materials are placed under an external magnetic field, the moments opposite to the field are induced. Such materials are called diamagnets. Diamagnetism is the response of the diamagnets when placed in an external magnetic field.
Diamagnetism was discovered by Anton Brugmans in 1778 when he observed that bismuth gets repelled by magnetic fields, thus theorizing that diamagnets get repelled by magnets.
Potential Due to a Magnetized Object01:24

Potential Due to a Magnetized Object

Magnetic dipoles in magnetic materials are aligned when placed under an external magnetic field. For paramagnets and ferromagnets, dipole alignment occurs in the direction of the magnetic field. However, the dipoles align opposite to the field in the case of diamagnets. This state of magnetic polarization due to the external field is called magnetization. Magnetization is defined as the dipole moment per unit volume. It plays a similar role to polarization in electrostatics.
The vector...
Paramagnetism01:30

Paramagnetism

Paramagnets are materials with unpaired electrons that possess a finite magnetic moment. In the absence of a magnetic field, these moments are randomly oriented, and thus the net moment is zero. Under an external field, a torque acting on the moments tends to align them along the field's direction. However, the random thermal motion of electrons produces a torque opposite to the external field and tries to disorient the moments. These two competing effects align only a few moments along the...
Induced Electric Dipoles01:28

Induced Electric Dipoles

A permanent electric dipole orients itself along an external electric field. This rotation can be quantified by defining the potential energy because the external torque does work in rotating it. Then, the potential energy is minimum at the parallel configuration and maximum at the antiparallel configuration. While the former is a stable equilibrium, the latter is an unstable equilibrium.
Since the absolute value of potential energy holds no physical meaning, its zero value can be chosen as per...
Toroids01:27

Toroids

A toroid is a closely wound donut-shaped coil constructed using a single conducting wire. In general, it is assumed that a toriod consists of multiple circular loops perpendicular to its axis.
When connected to a supply, the magnetic field generated in the toroid has field lines circular and concentric to its axis. Conventionally, the direction of this magnetic field is expressed using the right-hand rule. If the fingers of the right hand curl in the current direction, the thumb points in the...
Torque On A Current Loop In A Magnetic Field01:13

Torque On A Current Loop In A Magnetic Field

The most common application of magnetic force on current-carrying wires is in electric motors. These consist of loops of wire, which are placed between the magnets with a magnetic field. When current flows through the loops, the magnetic field applies torque, which causes the shaft to rotate, thus converting electrical energy to mechanical energy.
Consider a rectangular current-carrying loop containing N turns of wire, placed in a uniform magnetic field. The net force on a current-carrying loop...

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Related Experiment Video

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Simulation, Fabrication and Characterization of THz Metamaterial Absorbers
13:44

Simulation, Fabrication and Characterization of THz Metamaterial Absorbers

Published on: December 27, 2012

Toroidal dipolar response in a metamaterial.

T Kaelberer1, V A Fedotov, N Papasimakis

  • 1Optoelectronics Research Centre and Centre for Photonic Metamaterials, University of Southampton, Southampton SO17 1BJ, UK.

Science (New York, N.Y.)
|November 6, 2010
PubMed
Summary
This summary is machine-generated.

Researchers observed toroidal multipoles, a fundamental electromagnetic excitation, in a metamaterial. This provides the first direct experimental evidence of toroidal dipoles in classical electrodynamics.

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Area of Science:

  • Electromagnetism
  • Metamaterials Science
  • Particle Physics

Background:

  • Toroidal multipoles are fundamental electromagnetic excitations distinct from charge and magnetic multipoles.
  • While implicated in parity violation, direct experimental evidence in classical electrodynamics has been lacking.
  • Toroidal symmetry is prevalent in natural systems, particularly at the macromolecule level.

Purpose of the Study:

  • To provide direct experimental evidence for the existence of toroidal multipoles in classical electrodynamics.
  • To demonstrate a resonant electromagnetic response attributable solely to toroidal dipoles.
  • To highlight the potential significance of toroidal multipoles in both artificial and natural systems.

Main Methods:

  • Fabrication and characterization of an engineered metamaterial.
  • Measurement of the resonant electromagnetic response of the metamaterial.
  • Analysis of the response to distinguish it from charge and magnetic multipole contributions.

Main Results:

  • Observation of a distinct resonant electromagnetic response in the metamaterial.
  • The observed response could not be explained by conventional charge or magnetic multipoles.
  • The response was uniquely attributable to the presence of a toroidal dipole excitation.

Conclusions:

  • The experiment provides the first direct evidence of toroidal dipole excitations in classical electrodynamics.
  • Metamaterials can be engineered to exhibit toroidal responses, opening new avenues for electromagnetic applications.
  • Toroidal multipoles may play a more significant role in natural systems than previously recognized, especially in macromolecules.