Magnetic Field

Claimed by Seongshik Kim spring 2016

This page discusses the general properties and characteristics of magnetic fields

Magnetic Field

Unlike electric fields, magnetic fields are made by moving charges. Stationary charges do not exert magnetic fields. In equilibrium, there is no net motion of charges inside a metal. Therefore, it should be noted that electrons inside a metal must move continuously. This is the very basic definition of the current, a non-equilibrium system in which there is a constant flow of electrons in order to create a magnetic field.

There are a few important main concepts to understand before proceeding further. First, the direction of the magnetic field is perpendicular to the direction of the current. Second, equilibrium and being continuous are totally different things.

Dependence on frame of reference

Because the magnetic field relies on the velocity of a particle, it can vary with frame of reference. That is to say, one observer could observe a magnetic field while another does not observe a field due to the relative velocity of the particle. Consider a moving proton, a moving compass, and a stationary compass. The proton and moving compass are moving with identical velocity, so to the compass, the proton appears to be stationary ([math]\displaystyle{ \vec{v} = 0 }[/math]), so the observed magnetic field is is also 0. The stationary compass, however, observes a certain velocity so a magnetic field is observed.

Magnetic field due to a single charged particle

The magnetic field [math]\displaystyle{ \vec{B} }[/math] created by a single charged particle is given by the equation [math]\displaystyle{ \vec{B} =\frac{\mu_0}{4\pi} \frac{(q\vec{v} \times \hat{r})}{|\vec{r}|^2} }[/math], where [math]\displaystyle{ \frac{\mu_0}{4\pi} }[/math] is a fundamental constant equal to [math]\displaystyle{ 1 \times 10^{-7} T }[/math], [math]\displaystyle{ q }[/math] is the charge of the particle, [math]\displaystyle{ \vec{v} }[/math] is the velocity of the particle, and [math]\displaystyle{ \vec{r} }[/math] is the vector that points from source to observation location. This equation is called the Biot-Savarde law. You may notice that this equation involves a cross product.

Page initiated by --Spennell3 (talk) 14:20, 19 October 2015 (EDT)