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> The invention of the copy machine Issue: 2006-1 Section: Science


Can you imagine life without the copy machine? Probably not. Well who knew that this universally used and important office appliance was actually invented by a Bulgarian? Not many, and because of that we will introduce you to the man who helped make a small step for humanity and a huge are for Bulgaria. This man was Georgi Nadjakov who became one of the greatest inventors of modern times. And this is how he created the so called xerox. But who was the person behind this brilliant invention?


Georgi Nadjakov is one of the most famous Bulgarian physicists. He was born on December 26, 1896 in Dupnitza. There he studied maths and physics and graduated at the University of Sofia. After the first term he went to the army. There he gained officer's rank, taught recruits and took part in several campaigns. When he left the army, Nadjakov continued his studies. As a front-fighter he was credited with one term at the university each year in the army. In 1920 after attending lectures during only four terms, he finished his higher education. In 1921 the university appointed him physics assistant. His skills were recognized by the Faculty of Physics and Mathematics, which gave Nadjakovthe permission to study abroad with Marie Curie and Paul Langevin.

Before going to Paris he had never seen electrometers. To increase his knowledge he read books during the night and attended lectures at the Sorbonne and at the University of Paris. While at Langevin’s laboratory Nadjakov researched insulators and semi-conductors for a year. In addition to a grant the fund of University of Sofia gave him 5000lv. for materials. His results were published in Bulgaria and they were Georgi Nadjakov’s first scientific publication.

The Faculty of Physics and Mathematics elected Nadjakov associate professor in experimental physics. Throughout his work he kept experimental physics courses and an electrical engineering course, which included new demonstrations and laboratory experiments. He later became a professor in experimental physics.


Georgi Nadjakov was dean of the Faculty of Physics and the University of Sofia principal.

Together with his teaching activity he continued working on the photoelectric effects and discovered the photoelectric state of the substances. With this discovery he put his name in the world history of physics and technique. Until the end of his life he worked in this field of studies – he worked out and built new types of electrometers and for some of them he got a patent. Georgi Nadjakov gained international prestige and he awarded a lot of prizes. He died on February 24, 1981.



Academician Gerogi Nadjakov was the first to create a new standard physical apparatus. Those apparatus were mainly different kinds of electrometers. Four electrometers were original. He also suggested a new method of measurement.

Along with Vera Postampirova, Georgi Nadjakov invented a new electrometer system. He also found a common formula about all electrometers created by him. He built a complicated surface of a quadrant with collaborators. Dependence between deviation of a needle and potential of a measure quadrant was linear in the new electrometer.


Photo electrets

On September 1925 the Bulgarian physicistGeorge Nadjakov arrived in Paris and went to Paul Langevin to ask him to work in his laboratory. He wanted to work on the photoelectrical effect. After his work in Paris he went back to Bulgaria and continued working on the photo electrets. In 1937 he discovered permanent internal photo-polarization. He used light and electricity for making the electrets. The new electrets was called photo-electrets. The previous type of electrets, which was obtained by heat and electricity was called by him thermoelectric.

On 22ndJune 1937, the considered date of the discovery, Paul Langevin reported to the French Academy of Science. Announcements for the discovery were published in the magazine of the Academy (Sur une nouvelle espèce de polarisatiron permanente des dielectriques) and in the German magazine Physikalische Zeitschrift.

The discovery of the photoelectric state was the most considerable result of George Nadjakov. He legitimated his authorship in Bulgaria only in 1981. Why did he wait so long to legalize his discovery in his own country? He explained: I was waiting to see what application it will find. Now his discovery is on the first place in the Golden book of the Bulgarian discoverers and inventors.


Applications of Nadjakov’s discoveries

Researching groups in Russia, Japan, Brazil and United States started scientific works. The discovery became the base for the development of the classic electro photography. It is put into practice in the production of the copy machine and photos from space satellites and in the sphere of non vacuum television techniques, memory devices, etc.

The interest to the photoelectrical effects and semi-conductors increases. We will end the article with Nadjakov’s words: I had my own idea. And this is the most important thing. You can have the most expensive devices, the most modernistic apparatus, but if you don’t have your own idea, you will not make a discovery. So let’s follow our ideas. They can turn into something good, interesting and useful.




  • A.Vavrek, Half century from the discovery of the photoelectrets, Association of the physicists in Bulgaria, 1986, book 4, pages 36-40
  • Science and life № 10, 2002, 111-115



  • eDecember 10, 2004