(ii) Which statements are correct regarding the ferromagnetic materials? (6 marks). (a) Coercivity is the measure of how

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Ii Which Statements Are Correct Regarding The Ferromagnetic Materials 6 Marks A Coercivity Is The Measure Of How 1 (68.86 KiB) Viewed 43 times

(ii) Which statements are correct regarding the ferromagnetic materials? (6 marks). (a) Coercivity is the measure of how easily the magnetization of the material is affected by the external magnetic field. (b) Soft magnetic materials have coercivity lower than 1 Tela. (c) Using a material with high uniaxial magnetocrystalline anisotropy can increase coercivity. (d) Permanent magnets can achieve their resistance to demagnetization because of pinning of the domain walls. (e) All permanent magnets are difficult to be magnetized because of high coercivity.
(iii) Which statements are correct regarding the hard and soft ferromagnetic materials? (8 marks) (a) The soft or hard materials are classified based on B-H behaviours. (b) Soft ferromagnetic materials are easy to magnetize and demagnetize and hence required a relatively low external magnetic field, resulting in narrow B-H loops and low magnetization. (c) Hard ferromagnetic materials are difficult to magnetize and demagnetize with broad B-H loops. (d) Soft ferromagnetic materials can be found in applications including electric motors, transformers, and inductors. (e) Hard ferromagnetic materials are used as permanent magnets in various applications such as MRI.
(A) Which statements are correct regarding type I and type II superconductors? (6 marks). (a) Type I superconductor has only one critical magnetic field. When the magnetic field is larger enough, the superconductivity suddenly disappears. (b) Normally, type I superconductor is a pure metal, such as Pd, Hg, or Al, etc. (c) Type II superconductors have at least two critical points. (d) In one range of magnetic field, the superconductive state can be replaced by the vortex state. (e) The critical field for type II superconductor is higher than type I superconductor.
(B) Which statements are correct regarding the Meissner effect? (5 marks). (a) Meissner effect states that a superconductor below critical temperature will expel all magnetic field from the bulk of the sample as a perfect diamagnetic substance. (b) The direct phenomenon from Meissner effect is the levitation of magnet on the surface of superconductor. (c) Levitation is mainly observed in type I superconductors due to the fact that the critical field for type I superconductor is very small. (d) Some superconductors do not exhibit Meissner effect. (e) Meissner effect is used in Maglev trains.
(A) Which statements are correct regarding the Seebeck effect and the Peltier effect (6 marks). (a) Seebeck effect indicates that a thermoelectric voltage will be induced in a closed-loop made up of two dissimilar material of different temperatures. (b) Seebeck effect is caused by the lattice only. (c) By charge-carrier diffusion, the hot carrier tends to move to the cold end, inducing both a heat current and an electric current. (d) Peltier effect is the presence of heat at an electrified junction of two different materials. (e) Peltier effect is usually used for both heating and cooling.