( v) Isodynamic Line A line joining places of equal horizontal component of earth’ s magnetic field( H) is called an isodynamic line.
Magnetic Latitude
( i) If at any place, the angle of dip is δ and magnetic latitude is λ then tan δ = 2 tan λ
( ii) The total Intensity of earth’ s magnetic field I = I 0 √1 + 3 sin 2 λ where I o = M / R 3
It is assumed that a bar magnet of earth has magnetic moment M and radius of earth is R.
( Magnetic maps are maps obtained by drawing lines passing through different places on the surface of earth, having the same value of a magnetic element.)
Neutral Points
Neutral point of a bar magnet is a point at which the resultant magnetic field of a bar magnet and horizontal component of earth’ s magnetic field are zero.
When north pole of a bar magnet is placed towards south pole of the earth. then neutral point is obtained on axial line.
B = μ o / 4π 2Mr /( r 2 – l 2) 2 = H If r > > l, then B = μ o / 4π 2M / r 3 = H
When north pole of a bar magnet is placed towards north pole of the earth, then neutral point is obtained on equatorial line
B = μ o / 4π 2Mr /( r 2 + l 2) 2 = H If r > > l, then B = μ o / 4π 2M / r 3 = H
Tangent Law
When a bar magnet is freely suspended under the combined effect of two uniform magnetic fields of intensities B and H acting at 90 ° to each other, then it bar magnet comes to rest making an angle 0 with the direction of H, then
B = H tan θ