Portal:Electronics

Georg Simon Ohm, (March 16, 1789 - July 6, 1854) a German physicist, was born in Erlangen and educated at the university there. His most important finding was Ohm's Law, which he first published in his pamphlet Die galvanische Kette mathematisch bearbeitet, in 1827. This work, the germ of which had appeared during the two preceding years in the journals of Schweigger and Poggendorff, has exerted an important influence on the development of the theory and applications of electric current. Ohm's name was adopted as the SI unit of resistance, the ohm (symbol Ω).

In physics, Coulomb's law is an inverse-square law indicating the magnitude and direction of electrostatic force that one stationary, electrically charged object of small dimensions exerts on another. It is named after Charles-Augustin de Coulomb who used a torsion balance to establish it.

The magnitude of the electrostatic force between two point charges is directly proportional to the magnitudes of each charge and inversely proportional to the square of the distance between the charges.

For calculating the direction and magnitude of the force simultaneously, one will wish to consult the full vector version of the Law

${\displaystyle {\vec {F}}={\frac {1}{4\pi \epsilon _{0}}}{\frac {q_{1}q_{2}}{|{\vec {r}}|^{3}}}{\vec {r}}={\frac {1}{4\pi \epsilon _{0}}}{\frac {q_{1}q_{2}}{|{\vec {r}}|^{2}}}{\hat {r}}}$

where ${\displaystyle {\vec {F}}}$ is the electrostatic force vector, ${\displaystyle q_{1}}$ is the charge on which the force acts, ${\displaystyle q_{2}}$ is the acting charge, ${\displaystyle {\vec {r}}={\vec {r_{1}}}-{\vec {r_{2}}}}$ is the distance vector between the two charges, ${\displaystyle {\vec {r_{1}}}\ }$ is position vector of ${\displaystyle q_{1}}$, ${\displaystyle {\vec {r_{2}}}\ }$ is position vector of ${\displaystyle q_{2}}$, ${\displaystyle {\hat {r}}}$ is a unit vector pointing in the direction of ${\displaystyle {\vec {r}}}$, and ${\displaystyle \epsilon _{0}}$ is a constant called the permittivity of free space.

This vector equation indicates that opposite charges attract, and like charges repel. When ${\displaystyle q_{1}q_{2}\ }$ is negative, the force is attractive. When positive, the force is repulsive.

• ... that Helmut Reimer, who was professor of microelectronics at the Technische Universität Ilmenau from 1971, began in 1992 to make TeleTrusT a competence centre for applied cryptography and biometrics?
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Dell Computer's Inspiron laptop brand is a range of computers targeted at the consumer market. Current models in the range include the E1501/1501, E1405/640m, E1505/6400 and, E1705/9400. Some Inspiron machines offered in the past have been modified to become a higher or lower quality machine. An example of this is the first-generation Inspiron XPS and Inspiron 9100 (2004). Both machines shared the same options, Dell marked the XPS as an "ultimate gaming machine", while marking the 9100 as a "desktop replacement".