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## 4 Maxwell equations

The basic equations of electromagnetism which are collection of Gauss’s law for electricity ,Gauss’s law for magnetism ,Faraday’s law of electromagnetic induction and Ampere’s law for currents in conductors are called Maxwell’s equations.

These equations are part of comprehensive and symmetrical theory of electromagnetism,which is essential to understand electromagnetic waves,optics,radio and TV transmission,microwave ovens and magnetically levitated trains.

The four Maxwell’s equations for free space are:

## First Maxwell’s equation (Gauss’s law for electricity)

The Gauss’s law states that flux passing through any closed surface is equal to 1/ε0 times the total charge enclosed by that surface.

### Integral form of Maxwell’s 1st equation

It is the integral form of Maxwell’s 1st equation.

### Maxwell’s first equation in differential form

It is called differential form of Maxwell’s 1st equation.

## Second Maxwell’s equation (Gauss’s law for magnetism)

The Gauss’s law for magnetism states that net flux of the magnetic field through closed surface is zero because mono poles of magnet do not exist.

## Third Maxwell’s equation (Faraday’s law of electromagnetic induction )

According to Faraday’s law

It is the differential form of Maxwell’s third equation.

## Fourth Maxwell’s equation ( Ampere’s law)

The magnitude of the magnetic field at any point is directly proportional to the strength of the current and inversely proportional to the distance of the point from the straight conductors is called Ampere’s law.

Third Maxwell’s equation says that a changing magnetic field produces an electric field.But there is no clue in fourth Maxwell’s equation whether a changing electric field produces magnetic field ? To overcome this deficiency ,Maxwell’s argued that if a changing magnetic flux can produce an electric field then by symmetry there must exist a relation in which a changing electric field must produced a changing magnetic flux.