Electromagnet Notes
... the electrical current moving through a circuit moved the needle of a compass. When he reversed the current the needle was deflected in the opposite direction. When the current was cut off, the compass worked normally. Oersted hypothesized that the electrical current produced a magnetic field around ...
... the electrical current moving through a circuit moved the needle of a compass. When he reversed the current the needle was deflected in the opposite direction. When the current was cut off, the compass worked normally. Oersted hypothesized that the electrical current produced a magnetic field around ...
Slide 1
... The number of field lines passing through a surface is the magnetic flux The flux per unit area is proportional to the strength of the magnetic field. ...
... The number of field lines passing through a surface is the magnetic flux The flux per unit area is proportional to the strength of the magnetic field. ...
Chapter 9 Study Guide
... A device that measures current is called galvanometer. A coil of wire with a current is called a solenoid. A coil of wire with a ferromagnetic core and with a current is called an electromagnet. A device that converts mechanical energy into electrical energy is called a generator. The area of magnet ...
... A device that measures current is called galvanometer. A coil of wire with a current is called a solenoid. A coil of wire with a ferromagnetic core and with a current is called an electromagnet. A device that converts mechanical energy into electrical energy is called a generator. The area of magnet ...
Physics
... and that between two bar magnets Describe how to use two permanent magnets to produce a uniform magnetic field pattern. Understand that an electric current in a conductor produces a magnetic field round it describe the construction of electromagnets Sketch and recognise magnetic field patterns for a ...
... and that between two bar magnets Describe how to use two permanent magnets to produce a uniform magnetic field pattern. Understand that an electric current in a conductor produces a magnetic field round it describe the construction of electromagnets Sketch and recognise magnetic field patterns for a ...
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.