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Why should the material used for making permanent magnets have high coercivity?
The material should have high retentivity so that the magnet is strong and high coercivity so that the magnetisation is not erased by stray magnetic fields
What materials are used to build a magnet?
Materials with high coercivity and high retentivity.
How do you test for coercive?
the coercivity is test by drawing B-H curve.Coericivity is defined as without giving any magnitising force it will produce magnetic field intensity.
What has the author Urve Kangro written?
Urve Kangro has written: 'Divergence boundary conditions for vector helmholtz equations with divergence constraints' -- subject(s): Boundary conditions, Helmholtz equations, Coercivity, Boundary value problems, Divergence
What is used to make magnets?
A good permanent magnet should produce a high magnetic field with a low mass, and should be stable against the influences which would demagnetize it. The desirable properties of such magnets are typically stated in terms of the remanence and coercivity of the magnet materials.
Why does hard iron retain magnetism?
Coercivity is the property describing the ability of magnetic material to retain magnetism. Compared to soft iron, hard iron has larger magnetic domains, regions of the crystal where atomic magnetic fields have similar orientation. Materials with fewer, bigger domains within a given volume have higher coercivity than materials with many small domains. Hard iron can still lose its magnetism, as all permanent magnets can be demagnitized if strong enough fields are involved. Soft iron loses magnetism simply by removing it from a magnetic field. Some "rare earth" metal alloys can retain magnetism much better than hard iron, since they can have much larger domains.
Why Soft Iron is suitable for preparing pole pieces in earphones as well as loudspeakers instead of steel?
Soft iron is suitable for preparing pole pieces in headphones as well as loudspeakers instead of steel because soft iron materials have high permeability and low coercive force. They are easily magnetized and demagnetized. Examples of soft magnetic material are silica-steel (Fe-97 and Si-3), Sandust (Al-5, Si-10, Fe-85). Soft iron materials have following characteristics:- Thin hysteresis loop. High permeability. Low coercivity. High susceptibility. Low hysteresis loss. Low eddy current loss. Whereas materials made up of steel have totally different properties i.e. High permeability and High hysteresis loss. Large hysteresis loop. High coercivity residual magnetism.
What is supermalloy?
Supermalloy is a metal alloy that is 79% nickel, 5% molybdenum and 16% iron. It is used in mechanical and electronic components like hard drives. It is disigned to have a very high magnetic permeability and a low coercivity, meaning that magnetic fields can flow though it very easily. It is also a soft magnetic material, meaning that it doesn't stay magnetized itself once the magnetic field is removed.
Working principle of hysteresis motor?
A hysteresis motor operates on the principle of hysteresis loss in the rotor. It has a rotor made of high coercivity material like chrome steel, which exhibits significant hysteresis characteristics. The rotating magnetic field in the stator induces eddy currents in the rotor, causing it to lag slightly behind the field, resulting in continuous rotation.
How do magnetic stripes form?
Conclusions Strip with a porosity of 25%, when sintered at a temperature of 1200°C in hydrogen with a dewpoint of -30°C, is refined with respect to carbon and oxygen. At the lower sintering temperatures of 1000 and 1100°C, the carbon content is reduced to 0.03-0.02%; the quantity of not easily reducible oxides remains unaltered. With regard to the kinetics of grain growth, nonporous strip made from iron powder may be classed with steels which are coarse-grained by their prehistory.Porosity substantially affects the value of coercivity. Each 2% of pores increases the coercivity approximately by 0.1 oersted.If temperatures of 1200°C and above, with holding times of 2-3 hr are used for presintering, and temperatures of 900-1000°C for the final heat treatment of the nonporous strip, the magnetic properties of the strip can satisfy the requirements of GOST 3836-47 for low-carbon, electrical engineering thin sheet steel.
Why is soft iron used for the core of an electromagent?
The main advantage of an electromagnet is it can be turned on and off. Iron is a soft magnetic material an therefore looses its magnetism very quickly, if you use a metal like like steel it will not loose it magnetism very easily and even if you turn off the current it will remain a magnet.
When was the first ATM used for general public?
The first mechanical cash dispenser was developed and built by Luther George Simjian and installed in 1939 in New York City by the City Bank of New York,[citation needed] but removed after 6 months due to the lack of customer acceptance.Thereafter, the history of ATMs paused for over 25 years, until De La Rue developed the first electronic ATM, which was installed first in Enfield Town in North London, United Kingdom on 27 June 1967 by Barclays Bank. This instance of the invention is credited to John Shepherd-Barron, although various other engineers were awarded patents for related technologies at the time. Shepherd-Barron was awarded an OBE in the 2005 New Year's Honours List. The first person to use the machine was the British variety artist and actor Reg Varney. The first ATMs accepted only a single-use token or voucher, which was retained by the machine. These worked on various principles including radiation and low-coercivity magnetism that was wiped by the card reader to make fraud more difficult. The machine dispensed pre-packaged envelopes containing ten pounds sterling. The idea of a PIN stored on the card was developed by the British engineer James Goodfellow in 1965.
