Mar 162018
 

Today is the birthday (1789) of Georg Simon Ohm a Bavarian physicist and mathematician who gave his name to the equation relating voltage, resistance, and current: Ohm’s law. Ohm was born in Erlangen, Brandenburg-Bayreuth (then a part of the Holy Roman Empire), son to Johann Wolfgang Ohm, a locksmith and Maria Elizabeth Beck, the daughter of a tailor in Erlangen. Although his parents had not been formally educated, Ohm’s father was a respected man who had educated himself, and, in consequence, was able to give his sons an excellent education through his own instruction. Of the seven children of the family only three survived to adulthood: Georg Simon, his younger brother Martin, who later became a well-known mathematician, and his sister Elizabeth Barbara. His mother died when he was ten.

From early childhood, Georg and Martin were taught by their father who brought them to a high standard in mathematics, physics, chemistry and philosophy. Georg attended Erlangen Gymnasium from age 11 to 15 where he received little in the area of scientific training, which sharply contrasted with the inspired instruction that both he and his brother received from their father. Ohm’s father, concerned that his son was wasting his educational opportunity, sent him to Switzerland, where in September 1806 he accepted a position as a mathematics teacher in a school in Gottstadt bei Nidau. Ohm left his teaching post in Gottstatt Monastery in March 1809 to become a private tutor in Neuchâtel. For two years he carried out his duties as a tutor while and continued his private study of mathematics. Then in April 1811 he returned to the University of Erlangen.

Ohm’s own studies prepared him for his doctorate which he received from the University of Erlangen on 25th October 1811. He immediately joined the faculty there as a lecturer in mathematics but left after three terms because of unpromising prospects. He could not survive on his salary as a lecturer. The Bavarian government offered him a post as a teacher of mathematics and physics at a poor-quality school in Bamberg which Ohm accepted in January 1813. Unhappy with his job, Georg began writing an elementary textbook on geometry as a way to prove his abilities. That school was closed in February 1816. The Bavarian government then sent Ohm to an overcrowded school in Bamberg to help out with the teaching of mathematics.

After his assignment in Bamberg, Ohm sent his completed manuscript to King Wilhelm III of Prussia. The King was impressed with Ohm’s book, and offered him a position at the Jesuit Gymnasium of Cologne on 11th September 1817. This school had a reputation for good science education and Ohm was required to teach physics in addition to mathematics. The physics laboratory was well equipped, allowing Ohm to begin experiments in physics. As the son of a locksmith, Ohm also had some practical experience with mechanical devices.

Ohm published Die galvanische Kette, mathematisch bearbeitet (The Galvanic Circuit Investigated Mathematically) in 1827. Ohm’s law [current (I) = voltage (V) divided by resistance (R)] first appeared in this book, as did his comprehensive theory of electricity. The book begins with the mathematical background necessary for an understanding of the rest of the work. While his work greatly influenced the theory and applications of current electricity, it was coldly received at that time. It is interesting that Ohm presents his theory as one of contiguous action, a theory which opposed the concept of action at a distance. Ohm believed that the communication of electricity occurred between “contiguous particles” which is the term he himself used. The paper is concerned with this idea, and in particular with illustrating the differences in this scientific approach of Ohm’s and the approaches of Joseph Fourier and Claude-Louis Navier.

Ohm’s college did not appreciate his work and so he resigned from his position. He then made an application to, and was employed by, the Polytechnic School of Nuremberg. Ohm arrived at the Polytechnic School of Nuremberg in 1833, and in 1852 he became a professor of experimental physics at the University of Munich.

In 1849, Ohm published Beiträge zur Molecular-Physik, ( Molecular Physics). In the preface of this work he stated he hoped to write a second and third volume “and if God gives me length of days for it, a fourth”. However, on finding that an original discovery recorded in it was being anticipated by a Swedish scientist he did not publish it, stating: “The episode has given a fresh and deep sense for my mind to the saying ‘Man proposes, and God disposes’. The project that gave the first impetus to my inquiry has been dissipated into mist, and a new one, undesigned by me, has been accomplished in its place.”

Ohm died in Munich in 1854 and is buried in the Alter Südfriedhof. Ohm’s name has been incorporated in the terminology of electrical science in Ohm’s Law, and adopted as the SI unit of resistance, the ohm (symbol Ω). Although Ohm’s work strongly influenced theory, at first it was received with little enthusiasm. However, his work was eventually recognized by the Royal Society with its award of the Copley Medal in 1841. He became a foreign member of the Royal Society in 1842.

Knieküchle is a traditional Franconian fried dough pastry that is very popular in Old Bavaria as well. Depending on region it has several other names, including Auszogne, Krapfen, Küchl, or Rottnudel. As a general rule they are made of yeast dough but some recipes vary slightly. Very common for example is the addition of raisins. The dough is shaped so it is very thin in the middle and thicker on the edges. They are then fried in lard and dusted with confectioner’s sugar. The pastry is mostly eaten for celebrations, so it is appropriate today to celebrate Ohm. In Franconia, people differentiate between “Catholic” and “Protestant” Knieküchle depending whether it is dusted with confectioner’s sugar or not. Ohm was Protestant, so you decide.

Knieküchle

1 ¼ sticks unsalted butter
4 eggs
2 cups milk
½ cup sugar
salt
1 package yeast
3 cups (approx.) all-purpose flour
oil for frying (or lard)
powdered sugar

Instructions

In a small bowl, combine the yeast and ½ cup of the milk (lukewarm). Mix in 3 tablespoons flour and 1 teaspoon of the sugar. Allow this mixture to sit in a warm place for 1 hour.

Combine the remaining dough ingredients then add in the yeast mixture. Mix until a smooth dough forms, adjusting the flour as necessary. Knead by hand for about 20 minutes.

Place the dough in a lightly greased bowl, cover, and let sit in a warm place until double in volume.

Punch the dough down and divide it into tablespoon size pieces. Press each piece of dough flat and allow them to rise again for 1 hour.

Heat the oil in a deep-fryer to around 370˚F/190˚C.

Take each piece of dough and stretch it out again – large enough that it would be able to cover your knee [why they are called “knee pastries]. Fry each stretched-out piece of dough until golden brown on both sides. Remove from the oil with a slotted spoon and let drain on wire racks. Dust with powdered sugar if you wish. They can be eaten plain or with fruit preserves. They are best served warm.

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