Fundamentos de electronica, Apuntes de Electrónica Analógica

¡Descarga Fundamentos de electronica y más Apuntes en PDF de Electrónica Analógica solo en Docsity! Amperes Law The magnetic field in space around an electric current is proportional to the electric current which serves as its source, just as the electric field in space is proportional to the charge which serves as its source. Ampere's Law states that for any closed loop path, the sum of the length elements times the magnetic field in the direction of the length element is equal to the permeability times the electric current enclosed in the loop. In the electric case, the relation of field to source is 2 BA! = ui quantified in Gauss's Law which is a very powerful tool for calculating electric fields, Applications for Ampere's Law Magnetic field inside a long solenoic. 7 _ Magnetic field inside a toroidal coil. Magnetic field from Magnetic along field straight inside a wire, conductor. 1 Ohm's Law For many conductors of electricity, the electric current which will flow through them is directly proportional to the voltage applied to them. When a microscopic view of Ohm's law is taken, it is found to depend upon the fact that the drift velocity of charges through the material is proportional to the electric field in the conductor. The ratio of voltage to current is called the resistance, and if the ratio is constant over a wide range of voltages, the material is said to be an "ohmic" material. lf the material can be characterized by such a resistance, then the current can be predicted from the relationship: Kirchoffs Laws Connections between individual ports can be made through an appeal to Kirchoff's Laws, which specify two important connection rules. Kirchoff's Voltage Law (KVL) states that for a series connection, the currents will be equal in all ports to be connected, and that the sum of the voltages at all ports is zero, or, in other words, if we have a series connection of N ports. 4727 + D, +0, + 2 +v/=0 Kirchoff's Current Law (KCL) specifies the dual relationship among the voltages and currents in the case of a parallel connection of N ports. VD =D. VU Kirchhoff's Current Law Voltage Va source (V,) | ALL LALA, VyHVAV, 4 V, +, + V,+V,- V,=0 Thévenin's Theorem The idea here is that any two terminal network containing voltage and current sources, together with other linear circuit elements, such as resistors, has exactly the same electrical characteristics as an equivalent circuit consisting of a single voltage source in series with a single resistor. The Thévenin voltage is equal to the open circuit voltage seen at the output terminals of the linear circuit. The Thévenin resistance ¡is given in terms of the open circuit voltage and the short circuit current. Another way of expressing this, which is often used in practice, is to say