Champs statiques

1. What are static electric and magnetic fields?

Electric and magnetic fields are invisible lines of force generated by natural phenomena such as the Earth’s magnetic field or lightning, but also by human activities, mainly through the use of electricity.

• An electric field is the force field created by the attraction and repulsion of electric charges (the cause of electric flow), and is measured in volts per meter (V/m).
• A magnetic field is a force field created by a magnet or as a consequence of the movement of the charges (flow of electricity). The magnitude (intensity) of a magnetic field is usually measured in Tesla (T or mT).

The term static refers to a situation where the fields do not vary with time. Static electric and magnetic fields are two distinct phenomena, both characterized by steady direction, flow rate and strength (thus a frequency of 0 Hz).

• A static electric field (also referred to as electrostatic field) is created by charges that are fixed in space;
• A static magnetic field is created by a magnet or charges that move as a steady flow (as in appliances using direct current).

In contrast, time-varying electromagnetic fields, which reverse their direction at a regular frequency, are produced by appliances using alternating current (AC) as well as by cellular telephone antennas, microwaves, etc. In this case, the electric and magnetic fields are interrelated and are both associated with a specific frequency.

Both electric and magnetic fields weaken with distance from the source. More...

(For more information on low frequency fields,see our study on Power lines.)