Magnetic elements of earth Declination (θ), Dip (δ) & Horizontal component (BH) are called magnetic elements of earth as earth’s magnetic field can be completely defined in both magnitude & direction by knowing these three.
Geomagnetism 1. Study of magnetic field of earth is called Geomagnetism or terrestrial magnetism. 2. William Gilbert (in about 1600) was the first to demonstrate that the entire earth behaves as an enormous magnet. 3. The magnitude & direction of Earth’s magnetic field can be obtained approximately by assuming that the earth has a magnetic […]
Dipole’s natural alignment Any magnetic needle (or a dipole) free to move in a region of external magnetic field aligns so that its dipole moment become parallel to external magnetic field i.e. i.e. the position of stable equilibrium. This is because the position of stable equilibrium is the position of maximum stability or minimum potential […]
Superconductors: Perfect diamagnetics For super conductors cooled to very low temperatures χ = –1 & μr = 0. Thus the super conductors are perfect diamagnetic materials. The phenomenon of perfect diamagnetism in superconductors is calledthe Meissner effect. In superconductors the field lines are completely expelled. Also a superconductor repels a magnet and (by Newton’s third […]
Magnetic screening Magnetic field inside a ferromagnetic substance e.g. soft iron is zero. Thus any object can be saved from magnetic field by placing it inside a ferromagnetic cavity. This is called magnetic screening or shielding.
Ceramics Or ferrites (usually brittle) are made by heat & pressure treatment from the powders of BaO & FeO. Used to coat tapes for tape recorders & as computer memory stores.
Magnetic keepers The bar magnets are stored in pairs with their opposite poles together & a soft iron piece across them called magnetic keepers and used to make the circuit continuous, so that no free pole is left to cause demagnetize) in order to retain the magnetism. As otherwise they may demagnetize each other. Also […]
Electromagnets Core of electromagnets are made of ferromagnetic materials which have high permeability and low retentivity. Soft iron is a suitable material for electromagnets. On placing a soft iron rod in a solenoid and passing a current, we increase the magnetism of the solenoid by a thousand fold. When we switch off the solenoid current, […]
Permanent magnets The materials used in making permanent magnets should have high retentivity, high coercivity & high permeability. High retentivity makes the magnet is strong and high coercivity ensures the magnetisation is not erased by stray magnetic fields, temperature fluctuations or minor mechanical damage. Suitable materials for permanent magnets are steel, alnico, cobalt steel and […]
Corecivity (oc): The value of –H which has to be applied to a magnetic material so as to reduce residual magnetism to zero. The area of hysteresis loop is proportional to the thermal energy loss per unit volume for one hysteresis cycle of magnetization & demagnetization. Thus in order to minimize the energy losses that […]
Our objective is to create a situation where students will find Physics interesting & the strongest subject helping them to achieve top ranks in competitive exams.
Copyright © 2021 KP Institute of Physics | Powered by RiAcub
Call 9872662552