Electromagnetic field

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The electromagnetic field belongs to the range of non-ionizing radiation . A distinction is made between these fields in electromagnetic high-frequency and low-frequency. Compared to low-frequency fields, high-frequency fields are characterized by a higher frequency and thus a shorter wavelength .

Low frequency fields

In the electromagnetic spectrum , the low-frequency electric and magnetic fields are located in the frequency range between about 1 Hertz and <9 kilohertz . In contrast to high-frequency electromagnetic fields, with low-frequency fields there are significantly fewer changes in direction of the electric field and the magnetic field. In everyday life, low-frequency electric and magnetic fields occur in the following areas:

• the power supply (e.g. high-voltage lines ), frequency 50 Hz
• Household appliances and electrical installations in the house
• electrified transport systems such as railways , frequency 16.7 Hz

High frequency fields

The use of modern radio technologies creates high-frequency electromagnetic fields in the human environment. In the electromagnetic spectrum, the high-frequency electromagnetic fields are located in the frequency range between about 100 kilohertz and 300 gigahertz . In contrast to low-frequency fields, in high-frequency fields, both the electric field and the magnetic field change direction between tens of thousands and several billion times a second. As a result, there is a very close coupling of magnetic and electrical components.

High-frequency electromagnetic fields are used to transmit images, sound and data in the following modern means of communication :

• Radio and television
• Cordless phones ( DECT )
• Cellular
• Baby monitor
• Wireless LAN (WLAN) and Bluetooth for networking computers with each other and with peripheral devices
• The police and fire brigade use their own TETRA radio network for communication over longer distances.

Emergence

The field is excited in an oscillating circuit . The electrical energy in this resonant circuit shifts between the electrical field and the magnetic field. A capacitor for the electric field and a coil for the magnetic field serve as energy storage . The rhythm of this shift is called frequency (Hz).

The electromagnetic alternating field has the property of leaving the resonant circuit via an antenna and radiating into the room as an electromagnetic wave ( transmission system ).

However, it is wrong to assume that an electromagnetic wave is only released from an antenna in the HF range (high frequency) from 30 kHz. "Longest waves (Very Low Frequency VLF for short, not to be confused with longitudinal waves) are electromagnetic waves in the frequency range below 30 kHz." (See: Longest wave )

Effects

Electromagnetic fields belong to non-ionizing radiation. In contrast to ionizing radiation, the photons of non- ionizing radiation do not have enough energy to ionize atoms and molecules , i.e. to knock electrons out of the shell and thus generate positively charged particles ( cations ). Among other things, this means that, in contrast to X-rays, for example, their energy is too low to damage the genetic material directly and thus be directly involved in the development of cancer .

However, electromagnetic fields can cause damage to health in other ways:

• Low-frequency electric and magnetic fields can generate electric fields and currents in the body.
• Biological tissue can be heated by high-frequency electromagnetic fields .

Electromagnetic fields in the workplace

The exposure of employees to electromagnetic fields at office workplaces through the electrical devices (computers, screens) available there is negligible due to the low field strengths. For other field sources, e.g. B. on systems for inductive hardening and melting or on welding equipment, much higher frequencies and field strengths are possible, which require closer examination.

The results of the calculation or measurement of electromagnetic fields at the workplace form the basis for assessing possible hazards for employees at the workplace and for determining protective measures. Workplaces of employees with passive or active implants must always be considered separately in the risk assessment.

The research report "Electromagnetic Fields in the Workplace" offers further information on the physical and physiological background of exposure to electromagnetic fields.

A technical assessment of the existing workload can be carried out with the questionnaire "EMF assessment" based on the guidelines of the EU Commission. A recommendation for the further course of action and possible protective measures can be expressed in Directive 2013/35 / EU.

exploration

In 1888, the German physicist Heinrich Hertz was able to demonstrate experimentally the electromagnetic wave theoretically predicted by James Clerk Maxwell . In February 1892 Sir William Crookes wrote under the title "Some Possibilities of Electricity": "There is the possibility of telegraphy without wires." The Englishman Preece demonstrated this in 1896 in London with the help of a Marconian transmitter and receiver.

Other people who were involved in research into the electromagnetic alternating field and the electromagnetic wave:

• 1890 - Édouard Branly - Physicist and Chemist - Paris
• 1890 - Sir Oliver Lodge - Professor - England
• 1894 - Professor Augusto Righi - University of Bologna - Lecture on electromagnetic waves
• 1894 - Guglielmo Marconi (1874–1937) - University of Bologna - participant in the lecture
• 1895 - Alexandr Popow - 250 m wireless transmission between transmitter and receiver
• 1896 - Guglielmo Marconi (born 1874) - British patent (No. 12039) in the field of wireless telegraphy
• 1882 - William Henry Preece, Faraday
• 1897 - William Henry Preece, Faraday, Adolf Slaby - 5.5 km radio link
• May 13th, 1897 birth of wireless telegraphy
• 1901 - Guglielmo Marconi (born 1874) - bridges the Atlantic by radio

Individual evidence

1. ^ ^{A b} Institute for Occupational Safety and Health of the German Social Accident Insurance (IFA): Electromagnetic Fields - Topics and Projects. Retrieved February 12, 2019 . 
2. ↑ Federal Ministry of Labor and Social Affairs (BMAS): Research report "Electromagnetic fields in the workplace". Retrieved February 12, 2019 . 
3. ↑ EU Commission: EMF assessment. emfeld GmbH, accessed on July 3, 2019 .