Electromagnetism

According to Ampere’s Circuital Law, the magnetic field around a long straight conductor carrying current at a distance is given by:
Since the magnetic flux density represents the same quantity.

The formula for the self-inductance of a solenoid is:
where:
- is the permeability of free space,
- is the number of turns,
- is the cross-sectional area,
- is the length of the solenoid.

The relation between polarization ** and **electric susceptibility is: where:
- is the permittivity of free space,
- is the applied electric field.