1. What are electromagnetic fields?

Electric current and voltage produce magnetic and electric fields, respectively. These fields exert forces on electric and magnetic particles.

When an electric cable, machine or device is connected to the mains, it gets energised and, thus, generates an electric field. The electric field exists even when the appliance is turned off and no current circulates.

Switching on the device produces, in addition to the electric field, a magnetic field. Magnetic fields are generated when current circulates. Magnetic fields penetrate walls, ceilings, or windows almost undamped.

Electric and magnetic fields have the following two characteristics:

• Field strengths increase with rising voltage and current.
• Field strengths decrease with increasing distance to the source.

Static fields are generated by batteries or by electrostatic charging. Their field strength is constant over time. Alternating or time-varying fields change their field strengths periodically: they oscillate with a specific frequency. Alternating fields are divided into low-frequency and high-frequency fields. Sources of low-frequency fields are: mains power (50Hz; Hz=Hertz; 50 oscillations per second) and railway power (16 2/3 Hz).

We talk of high-frequency fields, when the frequency exceeds 100,000 oscillations per second (100kHz; kHz=Kilohertz). High-frequency fields can be propagated by antennae. That's why all radio applications (radio, TV, mobile communication, radio link systems, GPS, etc.) are located in the high-frequency range.

Upper limit for high-frequency is 300 billion Hertz (300GHz; GHz=Gigahertz). Beyond, we speak of infrared.

The ordinary language word «electro smog» mostly refers to technically generated electric and magnetic fields. Standard term, however, is EMF (electromagnetic fields). EMF has not enough energy to destroy («ionise») chemical bonds (molecules) in organic tissue. Therefore, these fields are also called «non-ionising fields» or «non-ionising radiation».

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