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Electric, magnetic and electromagnetic fields in everyday life
- Physical basics
- Electromagnetic fields in the human environment

Historical review

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The existence of static electric and magnetic fields has long been known. As an example, ancient Greece experiments with amber and cat fur on static electricity were passed on. From that period, also therapeutic treatments with electric fields of the electric ray are described. In China, 3000 years ago, the magnetic field of the earth was used as a compass. But these effects, as well as the electric phenomenon of lightning, were not really understood by these ancient societies.

In the 17th and 18th centuries people started to analyze these phenomena with more scientific approaches. Friction machines (the first electrostatic generators) and batteries were developed. Benjamin Franklin invented the lightning conductor, and Luigi Galvani demonstrated the important role of electrical processes for living beings in his experiments with frogs' legs, published in 1791. In the 19th century, more elaborate experiments were conducted by Hans Christian Oersted, Michael Faraday, André-Marie Ampère, Georg Simon Ohm, Joseph Henry, Heinrich Hertz and others, which lead to a better understanding of electric and magnetic fields. Around 1860, James Clerk Maxwell successfully integrated all electric and magnetic phenomena into a single system of equations called “Maxwell equations”, which provided the basis for understanding all other electromagnetic processes. In 1887, the electromagnetic waves, theoretically introduced by Maxwell, were experimentally confirmed by Hertz.

Due to the growing knowledge of electric and magnetic processes, people started using these phenomena in technical developments such as electroplating, telegraphy and electric light. The first public carbon arc lamps were used for the first time around 1810. In the year 1880, Thomas Alva Edison introduced the incandescent lamp. In 1882 the first public electricity grid was installed in New York to enable the use of incandescent lamps. At approximately the same time, current generators and electric motors were developed, e.g. by Werner Siemens. The first electric tramway was put into operation in 1881 in Berlin. In 1887, about 2,000 electric motors existed in the USA; in 1889, their number reached more than 18,000.

The first national grids were powered by block-type direct current (DC) generator stations that were located in the cities. Due to large line losses, it was not possible in those days to transfer electricity over long distances. With the use of alternating current (AC) through transformers and high voltage power lines, energy could be transferred over long distances with small conduction losses. In 1891, the first 15 kV three-phase high voltage AC power line was built in Germany from the hydroelectric power plant in Lauffen am Neckar (today county of Heilbronn) with a length of 175 km ending in Frankfurt.

In 1890, almost 96% of the worldwide electricity consumption was used for lighting. In 1900, the percentage went down to 53 %. In 2013, the percentage of electricity used for lighting in Germany was only about 9 % of the total electricity consumption of 596 billion kilowatt hours (kWh). In 2012, approx. 47 % was consumed by the industry, 26 % was used by private households, 14 % by trade and businesses, 9 % by public institutions, 2 % by agriculture, and 3 % was used by transport, including railway.

The difference in use and number of line-operated technical devices has escalated rapidly in the last decades. Private households use a multitude of electrical appliances, e.g. electric kitchen stove, washing machine, radio, television, computers, dryers, microwave ovens, etc. The number of electrical appliances in businesses, industry and medicine is vast. Other examples of rapid development of new technologies that release electromagnetic radiation into the environment are mobile telephony and other radio communication technologies, as e.g. WiFi.

Electricity and its wide range of applications radically changed the conditions of human life in only about 100 years.

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Glossary: AC, carbon, Computers, current, DC, electric, electric fields, electromagnetic, electromagnetic waves, hertz, high voltage, human, lead, magnetic, magnetic field of the earth, magnetic fields, Maxwell, microwave ovens, power line, power plant, radio, static, television, therapeutic, transformers, WiFi