Magentism And Matter Flashcards
Properties of magnet
Attracts small pieces
Points in N-S direction
Always exists in pairs & no monopole exists
Induces magnetism in a magnetic substance placed near it(induction)
Magnetic poles
Regions where magnetic attraction is max
Magnetic axis
Line passing through poles of magnet
Magnetic equator
Line passing through center of magnet & perp to magnetic axis
Magnetic length(2l)
Dist btw 2 poles
m=
q(m)2l
Unit of m
A m²
Q(m) is
Pole strength
Bar magnet as equivalent solenoid
B = myu°/4pi 2m/r³
Prop of magnetic field lines
Forms continuous loop
Tan to field lines give direction of net B
Dotn intersect
Torque on dipole
mBsinø
Stable, unstable, max
P.E of magnetic Dipole
Work done is U
U = -mB[cosø2-cosø1]
Max, min, 0
Magnestising field
Magnetic field that exist in vacuum and induces magnetism
B°=myu°NI
Magnetic field intensity or magnetic intensity
No of ampere turns flowing per unit length
H=nI
H=B°/myu°
Intensity of magentisation
Magnetic moment developed per unit volume when placed in M.F
M=m(net)/V
M=q(m)/A Or M=nI(m)
Magnetic susceptibility X=
M/H
Ratio of intensity of magnetisation to magnetic field intensity
Magnetic permeability
Myu = B/H
Ratio of magnetic induction to magnetic intensity
Relative permeability
Myu(r) = myu/myu°
Relation btw M,H,khi(m)
B=myuH
H=nI
Khi=m/H
Diamagnetic
In uniform B, it is perp to B
In non-uniform B, move from strong to weak region
Expelled by external magnet
Weakly magnetized opp to B
Myu(r) < 1 (small +ve)
Myu < myu°
Weakly concentrated M.F.L
Khi is -ve
Khi(m) is independent of temp
Eg: h20,Cu,Zn,Ld,Gold,Si,NaCl,N, superconductors
Paramagnetic
In uniform B, it is || to B
In non-uniform B, move from weak to strong region
Weakly attracted by external magnet
Weakly magnetized || to B
Myu(r) > 1
Myu > myu°
Concentrated M.F.L
Khi is +ve
Khi(m) is inv prop to temp
Eg: manganese, Pt,AL,Chromium,CuCl,O2 ar stp, Na
Feromagnetic
In uniform B, it is || to B
In non-uniform B, move from weak to strong region
Strongly attracted by external magnet
Strongly magnetized || to B
Myu(r)»_space; 1
Myu»_space; myu°
Highly concentrated M.F.L
Khi»_space; 1
Khi(m) is dependent on temp
Eg: Lodestone, iron, Ni,Cobalt
Meismer effect
Phenomenon when a metal cooled yo a temp below it’s critical temp in B.F it attains both superconductivity & perfect diamagnetism. B gets completely expelled from it & repels a magnet. So Khi is -1 & myu(r) is 0.
Hard vs soft feromagnetic substances
Hard retain magnetism even after removal of ext B
Soft dont
Soft fero eg
Ni, cobalt, soft iron, temp magnets
Hard fero magnet eg:
Alnico,Lodestone, permanent magnet
Curie temp
Temp at which fero becomes para
In para, susceptibility varies with temperature khi(m) =
C/(T-T(c))
