Search research articles

ABOUT JoVE

Overview Leadership Blog JoVE Help Center

AUTHORS

Publishing Process Editorial Board Scope & Policies Peer Review FAQ Submit

LIBRARIANS

Testimonials Subscriptions Access Resources Library Advisory Board FAQ

RESEARCH

JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive

EDUCATION

JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site

Terms & Conditions of Use

Related Concept Videos

Magnetic Fields

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 Lines

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:

Plane Electromagnetic Waves II

Plane Electromagnetic Waves II

Consider a plane wavefront traveling in position x-direction with a constant speed. This wavefront can be utilized to obtain the relationship between electric and magnetic fields with the help of Faraday's law.

Atomic Nuclei: Nuclear Magnetic Moment

Atomic Nuclei: Nuclear Magnetic Moment

All atomic nuclei are positively charged. When they have a nonzero spin, they behave like rotating charges. As a consequence of their charge and spin, these nuclei generate a magnetic field (B). This, in turn, gives rise to a magnetic moment (μ), which is randomly oriented in the absence of an external magnetic field. When an external magnetic field (B0) is applied, the magnetic moment vectors can align with the field or against it in 2 + 1 orientations. A hydrogen nucleus, which is just a...

Divergence and Curl of Magnetic Field

Divergence and Curl of Magnetic Field

The magnetic field due to a volume current distribution given by the Biot–Savart Law can be expressed as follows:

Magnetic Field due to Moving Charges

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...

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by

Same author

Campanelli replies:.

Physical review letters·2013

Same author

Evolution of magnetic fields in freely decaying magnetohydrodynamic turbulence.

Physical review letters·2007

See all related articles

Search research articles

Related Experiment Video

Updated: May 8, 2026

Enhancement of the Initial Growth Rate of Agricultural Plants by Using Static Magnetic Fields

Enhancement of the Initial Growth Rate of Agricultural Plants by Using Static Magnetic Fields

Published on: July 8, 2016

Origin of cosmic magnetic fields.

Leonardo Campanelli¹

¹Dipartimento di Fisica, Università di Bari, I-70126 Bari, Italy. leonardo.campanelli@ba.infn.it

Physical Review Letters

|August 27, 2013

Summary

Quantum magnetic fluctuations during cosmic inflation do not decay as expected. These persistent fluctuations can explain the origin of large-scale magnetic fields observed in galaxies and galaxy clusters.

Area of Science:

Cosmology
Quantum Field Theory
Astrophysics

Background:

The origin of large-scale magnetic fields in the universe remains a significant unsolved problem.
Previous models assumed quantum magnetic fluctuations are diluted during cosmic inflation.

Purpose of the Study:

To calculate the quantum vacuum expectation value of the magnetic correlation function during de Sitter inflation.
To investigate the behavior of quantum magnetic fluctuations and their potential to seed cosmic magnetic fields.

Main Methods:

Calculation of the renormalized quantum vacuum expectation value of the two-point magnetic correlation function.
Analysis within the framework of free Maxwell theory in de Sitter spacetime.
Study of the quantum-to-classical transition of super-Hubble magnetic modes.

More Related Videos

Optimizing Magnetic Force Microscopy Resolution and Sensitivity to Visualize Nanoscale Magnetic Domains

Optimizing Magnetic Force Microscopy Resolution and Sensitivity to Visualize Nanoscale Magnetic Domains

Published on: July 20, 2022

Related Experiment Videos

Last Updated: May 8, 2026

Enhancement of the Initial Growth Rate of Agricultural Plants by Using Static Magnetic Fields

Enhancement of the Initial Growth Rate of Agricultural Plants by Using Static Magnetic Fields

Published on: July 8, 2016

Optimizing Magnetic Force Microscopy Resolution and Sensitivity to Visualize Nanoscale Magnetic Domains

Optimizing Magnetic Force Microscopy Resolution and Sensitivity to Visualize Nanoscale Magnetic Domains

Published on: July 20, 2022

Main Results:

Quantum magnetic fluctuations remain constant during inflation, contrary to adiabatic decay predictions.
Super-Hubble magnetic modes undergo a quantum-to-classical transition during inflation.
A scale-independent magnetic field of approximately 10^-12 G is predicted for an inflationary energy scale of 10^16 GeV.

Conclusions:

The persistence of quantum magnetic fluctuations during inflation provides a viable mechanism for generating primordial magnetic fields.
The calculated magnetic field intensity is consistent with observed galactic and galaxy cluster magnetic fields.
This work offers a potential solution to the origin of cosmic magnetism.