MAGNETISM

MAGNETISM MAGNETIC MOMENT : Pole Strength of each part m' = Magnetic moment of each part, When a bar magnet is cut into 'n' equal parts normal to its axis. Pole strength of each part m1 = m. Magnetic moment of each part M1 =  Length of each part 2l1 = . The force between two isolated magnetic poles is expressed by F =  Magnetic induction due to an isolated pole of strength 'm' is given by B =  Magnetic flux B = . 4. Magnetic flux density B = = =  MAGNETIC FLUX   = BA cos  Magnetic flux due to a magnet over a closed surface is zero  =  = 0 (Gauss' theorem in magnetism) TORQUE ACTING ON A BAR MAGNET IN A UNIFORM MAGNETIC FIELD. C = MB sin  and vectorially When  = 90° is maximum Cmax = MB If  = 90° and B = 1, C max = M The work done in deflecting a bar magnet through an angle from equilibrium position in a uniform magnetic field is W = MB (1 – cos  ). If  = 1800 W = 2MB (Maximum) P.E of the magnet = - = - MB Cos A bar magnet is under the influence of two magnetic fields At equilibrium C1 = C2 =  Force between two co-axial magnetic dipoles F =  The force between two magnets which are perpendicular to each other is F =  FIELD ON AXIAL LINE  In case of short bar magnet l < < d B =  Two magnets of different lengths having same moment are taken H =  Force experienced by a pole of pole strength 'm' placed at a point on the axial line of a short magnet F =  FIELD ON EQUITORIAL LINE B at any point on the equatorial line of a bar magnet is B =  In case of short magnet B =  VIBRATION MAGNETOMETER : The time period of vibrating T = where  Frequency of oscillation n =  Horizontal component of Earth's magnetic field: The magnetic dipole moment of current loop M = iA =  Bohr magneton M = n  here  Magnetic force B =  H. Intensity of megnetisation I =  v  volume of the material Curie constant