MHT-CET : Physics Entrance Exam

### MHT - CET : Physics - Magnetism Formulae Page 1

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1.

 Magnetic moment of a magnetic dipole: M = m × 2 l where m = pole strength of the dipole. 2l = magnetic length of the dipole. Direction of is from south pole to north pole.

2.

Magnetic induction ( ) at a point P at a distance of 'r' from centre of a short magnetic dipole:

B =

 m0 4p

(in magnitude)

Where

m0 = permeability of free space
M = Magnetic dipole moment of the dipole
q = angle between the line joining point P and the centre of the dipole and axis of the dipole.

Direction of at P is given by,

tan f

 1 2

tan q

The angle made by with axis of the dipole = f + q

Case I: If P is a point on the axis of the dipole, q = 0° or q = 180°

\ Baxis =

 m0 4p

 2M r3

; direction along the axis, parallel to

Case II: If P is a point on the equator of the dipole, q = 90°

\ Bequator =

 m0 4p

 2M r3

; direction parallel to the axis and opposite to .

3.

Magnetic potential (V) at a point P at a distance r from the centre of a short
magnetic dipole is given by,

V =

 m0 4p

 M cos q r2

Where

m0 = permeability of free space
M = Magnetic dipole moment
q = angle between the line passing through P and the centre of the dipole (O) and the axis of the dipole.

Case I:

If P is a point on axis,
q = 0° or q = 180°

Vaxis

 m0 4p

 M r2

(for q = 0°)

Or

Vaxis-

 m0 4p

 M r2

(for q = 180°)

Case II:

If P is a point on equator,
q = 90°
\ Vequator = 0

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