Electric and magnetic field transformations Picture: Consider inertial frames
... E’ = λ/(2πε0 r’) { (y’/r’) j + (z’/r’) k } On the other hand B’ = 0 because there is no current. The transformed fields (relative velocity = v i): Ex = E’x = 0 Ey = γ E’y Ez = γ E’z E = γλ/(2πε0 r’) { (y’/r’) j + (z’/r’) k } E = γλ/(2πε0 r) { (y/r) j + (z/r) k } ; this is the same as a line of charg ...
... E’ = λ/(2πε0 r’) { (y’/r’) j + (z’/r’) k } On the other hand B’ = 0 because there is no current. The transformed fields (relative velocity = v i): Ex = E’x = 0 Ey = γ E’y Ez = γ E’z E = γλ/(2πε0 r’) { (y’/r’) j + (z’/r’) k } E = γλ/(2πε0 r) { (y/r) j + (z/r) k } ; this is the same as a line of charg ...
Magnetic Field Lines, sketch Magnetic Field Lines, Bar Magnet
... • Direction is given by the direction a north pole of a compass needle points in that location • Magnetic field lines can be used to show how the field lines, as traced out by a compass, would look ...
... • Direction is given by the direction a north pole of a compass needle points in that location • Magnetic field lines can be used to show how the field lines, as traced out by a compass, would look ...
Homework #8: Magnetic Force and Biot-Savart Law
... one end in a uniform magnetic field ⃗⃗, which points into the page. a. [3 points] What current I in the loop would exactly balance the weight of the mass? b. [7 points] Suppose we now increase the current such that the magnetic force exceeds the weight of the mass. This causes the loop to rise and t ...
... one end in a uniform magnetic field ⃗⃗, which points into the page. a. [3 points] What current I in the loop would exactly balance the weight of the mass? b. [7 points] Suppose we now increase the current such that the magnetic force exceeds the weight of the mass. This causes the loop to rise and t ...
Superconductivity
Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature. It was discovered by Dutch physicist Heike Kamerlingh Onnes on April 8, 1911 in Leiden. Like ferromagnetism and atomic spectral lines, superconductivity is a quantum mechanical phenomenon. It is characterized by the Meissner effect, the complete ejection of magnetic field lines from the interior of the superconductor as it transitions into the superconducting state. The occurrence of the Meissner effect indicates that superconductivity cannot be understood simply as the idealization of perfect conductivity in classical physics.The electrical resistivity of a metallic conductor decreases gradually as temperature is lowered. In ordinary conductors, such as copper or silver, this decrease is limited by impurities and other defects. Even near absolute zero, a real sample of a normal conductor shows some resistance. In a superconductor, the resistance drops abruptly to zero when the material is cooled below its critical temperature. An electric current flowing through a loop of superconducting wire can persist indefinitely with no power source.In 1986, it was discovered that some cuprate-perovskite ceramic materials have a critical temperature above 90 K (−183 °C). Such a high transition temperature is theoretically impossible for a conventional superconductor, leading the materials to be termed high-temperature superconductors. Liquid nitrogen boils at 77 K, and superconduction at higher temperatures than this facilitates many experiments and applications that are less practical at lower temperatures.