EM basics-the Maxwell equations

All the important problem that the EM try to describe and explain is propogation and radiation of EM wave, on the BAS ICS of Maxwell equations. So we had to talk about the Maxwell equations, the greatest achievement in my opinion, first and then the propogation prob Lem and then, the radiation problem.

• 1 The Maxwell equations

In the more conditions,except in static electronic field or static magnetic field, the both are never exits indepently. The Maxwell equations is explicitly summarized the relationship between E and H, and between the source of them, a time- Varied electric current or a time-varied charge.

The first and equations are Gauss's law in E field and H field. That's, equation [1] is true at any point in space. That's, if there exists electric charge somewhere, then the divergence of D (electronic displacement vectors) at that poi NT is nonzero, otherwise it's equal to zero. Gauss ' Law states so electric charge acts as sources or sinks for electric fields.you see that both of these equations s Pecify the divergence of the field in question. For the top equation, we know this Gauss ' law for Electric fields states that the divergence of the Electric Flux Density D is equal to the volume electric charge density. But the second equation, Gauss ' magnetism law states the divergence of the magnetic Flux Density (B) is zero.

Why? Why isn ' t the divergence's B equal to the magnetic charge density?

Well-it is. But it just so happens that no one have ever found magnetic charge-not in a laboratory or on the street or on the subway. and therefore, until this hypothetical magnetic charge are found, we set the right side of Gauss to zero.

Faraday's law shows this a changing magnetic field within a loop gives rise to an induced current, which was due to a force or voltage within that circuit. We can then say the following about Farday's law:

Electric gives rise to magnetic fields. Magnetic fields around a circuit gives rise to electric current.

A magnetic Field changing in time gives rise to an e-field circulating around it.

A circulating E-field in time gives rise to a magnetic field changing in time.

A flowing electric current (J) gives rise to a magnetic Field this circles the current

A time-changing Electric Flux Density (D) gives rise to a magnetic field that circles the D field

Ampere's law and the contribution of Maxwell nailed down the basis for electromagnetics as we currently understand it. And so we know this a time varyingd gives rise to an H field, but from Farday's law we know that a varying H field gives R Ise to an E field .... and so forth and the electromagnetic waves propagate.

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EM basics-the Maxwell equations