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Related Concept Videos

Magnetic Fields01:27

Magnetic Fields

A moving charge or a current creates a magnetic field in the surrounding space, in addition to its electric field. The magnetic field exerts a force on any other moving charge or current that is present in the field. Like an electric field, the magnetic field is also a vector field. At any position, the direction of the magnetic field is defined as the direction in which the north pole of a compass needle points.
A magnetic field is defined by the force that a charged particle experiences...
Magnetic Field due to Moving Charges01:23

Magnetic Field due to Moving Charges

A stationary charge creates and interacts with the electric field, while a moving charge creates a magnetic field.
Consider a point charge moving with a constant velocity. Like the electric field, the magnetic field at any point is directly proportional to the magnitude of the charge and inversely proportional to the square of the distance between the source point and the field point. However, unlike the electric field, the magnetic field is always perpendicular to the plane containing the line...
Magnetic Field Lines01:19

Magnetic Field Lines

The representation of magnetic fields by magnetic field lines is very useful in visualizing the strength and direction of the magnetic field. Each of the magnetic field lines forms a closed loop. The field lines emerge from the north pole (N), loop around to the south pole (S), and continue through the bar magnet back to the north pole.
Magnetic field lines follow several hard-and-fast rules:
Magnetic Field of a Solenoid01:18

Magnetic Field of a Solenoid

A solenoid is a conducting wire coated with an insulating material, wound tightly in the form of a helical coil. The magnetic field due to a solenoid is the vector sum of the magnetic fields due to its individual turns. Therefore, for an ideal solenoid, the magnetic field within the solenoid is directly proportional to the number of turns per unit length and the current. Conversely, the magnetic field outside the solenoid is zero.
Consider a solenoid with 100 turns wrapped around a cylinder of...
Magnetic Field Of A Current Loop01:16

Magnetic Field Of A Current Loop

Consider a circular loop with a radius a, that carries a current I. The magnetic field due to the current at an arbitrary point P along the axis of the loop can be calculated using the Biot-Savart law.
Magnetic Susceptibility and Permeability01:31

Magnetic Susceptibility and Permeability

In linear magnetic materials, like paramagnets and diamagnets, magnetization is proportional to the magnetic field intensity. The constant of proportionality, a dimensionless number, is called magnetic susceptibility. The value of the susceptibility depends on the type of material.
When diamagnetic materials are placed under an external magnetic field, the moments opposite to the field are induced. Hence, the susceptibility for diamagnets has a minimal negative value of 10-5–10-6. Since...

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Related Experiment Video

Updated: Jun 30, 2026

Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples
07:01

Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples

Published on: June 9, 2016

Magnetic source separation in Earth's outer core.

Kenneth A Hoffman1, Brad S Singer

  • 1Physics Department, California Polytechnic State University, San Luis Obispo, CA 93407, USA. khoffman@calpoly.edu

Science (New York, N.Y.)
|September 27, 2008
PubMed
Summary
This summary is machine-generated.

Earth's axial dipole field originates separately from the nonaxial dipole (NAD) field. This geomagnetic field separation suggests distinct dynamo processes within the Earth's core.

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Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples
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Quantifying the Relative Thickness of Conductive Ferromagnetic Materials Using Detector Coil-Based Pulsed Eddy Current Sensors
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Quantifying the Relative Thickness of Conductive Ferromagnetic Materials Using Detector Coil-Based Pulsed Eddy Current Sensors

Published on: January 16, 2020

Area of Science:

  • Geophysics
  • Earth Science
  • Geomagnetism

Background:

  • The Earth's magnetic field is primarily generated by the geodynamo in the liquid outer core.
  • The geomagnetic field comprises an axial dipole component and a more complex nonaxial dipole (NAD) component.
  • Understanding the distinct sources of these components is crucial for interpreting paleomagnetic data and core dynamics.

Purpose of the Study:

  • To investigate the independence of the Earth's axial dipole field source from the nonaxial dipole (NAD) field sources.
  • To explore the implications of this independence for understanding the geodynamo and core-mantle interactions.
  • To provide a new framework for analyzing geomagnetic field behavior.

Main Methods:

  • Correlation analysis between the historic geomagnetic field structure and paleomagnetic field behavior.
  • Examination of precisely dated lava flows capturing periods of weak or absent axial dipole fields.
  • Geophysical modeling to infer the stratification of magnetic sources within the Earth's fluid core.

Main Results:

  • Evidence suggests the axial dipole field is largely independent of the sources generating the NAD field.
  • The axial dipole field appears significantly less influenced by the lowermost mantle compared to the NAD field.
  • A stratification of magnetic sources within the fluid core is proposed, with the axial dipole being a distinct layer.

Conclusions:

  • The Earth's axial dipole field and the nonaxial dipole (NAD) field originate from largely separate processes within the core.
  • The axial dipole field's relative immunity to lowermost mantle influences supports a stratified core dynamo model.
  • Future geomagnetic field models should account for this dichotomy in spatial-temporal dynamo processes.