1) The B-H curve for __________ will be a straight line passing through the origin
a) air
b) soft iron
c) hardened steel
d) silicon steel
2) For 1 m3 of material, the hysteresis loss will be minimum for
a) soft iron
b) steel
c) cobalt steel
d) silicon steel
3) The SI unit reluctance is
a) AT/Wb
b) AT/m
c) AT
d) N/Wb
5) The unit of relative permeability is
a) AT/m
b) N/Wb
c) AT/m2
d) a number
6) At high frequencies the material used for transformer cores is
a) silicon iron
b) soft iron
c) ferrite
d) none of the above
7) Out of the following materials, the area of hysteresis loop will be least for………
a) wrought iron
b) hard steel
c) silicon steel
d) soft steel
8) The magnetic material used for ……… should have a large hysteresis loop.
a) transformers
b) d.c generators
c) a.c motors
d) permanent magnets
9) The B-H curve of a ferromagnetic material is
a) linear
b) non-linear
c) circle
d) none of the above
10) The material used for the core of a good relay should have ……… hysteresis loop.
a) large
b) very large
c) narrow
d) none of the above
11) A permanent magnet should have
a) low remanence
b) high remanence
c) zero remanence
d) none of the above
12) The relative permeability of air is
a) 0
b) 1
c) infinite
d) none of the above
13) The curie tempareture of iron is
a) 2000C
b) 4300C
c) 7000C
d) 5500C
14) In practical magnetic circuits, the air-gap is kept
a) very small
b) large
c) very large
d) none of the above
15) An electromagnet uses
a) soft iron core
b) steel core
c) nickel core
d) copper core
16) The magnetic potential difference in a magnetic circuit is given by
a) H/I
b) B X I
c) HI
d) BI X h
17) The hysteresis loop of a material that cannot be magnetized easily is
a) narrow
b) very narrow
c) wide
d) none of the abve
18) The hysteresis loop is nearly square for
a) iron core
b) steel core’
c) ferrite core
d) wrought iron core
19) Due to fringing at the air gaps in a magnetic circuit, the effective area of the air gaps is
a) increased
b) decreased
c) same
d) none of the above