309. Q U I Z NO. 11 Magnets

Q U I Z   NO.  11

Magnets

1.      Highest magnetic  power … black whole

2.      The test for magnetic property is repulsion.

3.      Tesla – CGS system

4.      Gauss – FPS system

5.      Weber – SI system

6.      The value of g = …m/sec².

7.      10000 gauss = 1 Tesla

8.      Poles at the ends of a bar magnet.

9.      Poles lie outside of a spherical manget.

10.  Poles are at faces.

11.  If a magnet is spherical, the other end lies at imaginary point.

12.  Magnet cannot be magnetised beyond saturation point.

13.  Aristotle was the first to discuss on magnets. [625 to 545 BC]

14.  Sushruta was the first Indian to discuss about magnets.

15.  In China 4^th C BC – loadstone had magnetic properties. Shen Kuo [1031 – 954]

16.  Ferromagnetism was said Weiss.

17.  Ferro magnets are microscopic magnets.

18.  Ferro magnets are permanent magnets.

19.  Ferro magnets follow Curie Temperature.

20.  Ferro magnetic substances form alloys but are non-magnetic. Eg. Stainless steel

21.  Lanthanide elements exhibit strong Ferro magnets properties.

22.  Actinides exhibit Ferro magnetism at room temperature.

23.  Li gas exhibits Ferro magnetic property at below 1 K

24.  Ferro magnetism is due to 1] electron spin  2] Pauli’s exclusion principle

25.  Orbitals with partially filled shells/ unpaired spins can have magnetic moment.

26.  Ferro magnets spontaneously divide into magnetic domains due to lower energy configuration.

27.  In Ferro magnetic substances domains of different directions cancel out.

28.  Ferro magnetism is distinguished from para magnetism by permeability, remnance and coercivity.

29.  Curie Temp is only for Ferro magnetism.

30.  Curie temp. for Co is 1388^o K

31.  Curie temp. for F is 1043^o K.

32.  Curie temp. for Ni is 627^o K

33.  Above Curie temp. Ferro magnetic substances exhibit paramagnetic properties.

34.  Above Neel Temp. antiferromagnetic material becomes paramagnetic.

35.  Each ferrmagnet has a characteristic temp.

36.  Molecular field theory = ferromagnetism.

37.  Ferromagnetic material used for permanent magnet is above 1 weber/m².

38.  They present spontaneous magnetization.

39.  Ferromagnetism’s domain range is in the order of 10^-6 to 10^-2 cm³.

40.  In a domain of ferromagnetism the molecules range from 10¹⁷ to 10²¹.

41.  Fe, Co, Ni, Gd [gadolinium], magnetite [Fe₃O₄]

42.  If T < Of ferromagnetic behaviour.

43.  Below Curie Temp. ferromagnetic properties are exhibited by crystalline substances.

44.  Above Curie Temp. ferromagnetic substances lose their property.