ClassXII Physics Magnetism and Matter RN RWD

B2  0 3 4 d Magnetic moment of the current loop ˆ M  NIA  NIAn F = force (newton) m1 and m2 = pole strength (ampere metre) r = distance (metre) B1 = magnetic field strength (tesla) M = magnetic moment (ampere metre2) l = length of the bar magnet (metre) d = distance of the point from the bar magnet (metre) B2 = magnetic field strength (tesla) M = magnetic moment (ampere metre2) l = length of the bar magnet (metre) d = distance of the point from the bar magnet (metre) M = magnetic moment (ampere metre2) I = current (ampere) A = area (metre2) N = number of turns Torque acting on a magnetic dipole   MB sin  ˆ n = unit vector M = magnetic dipole moment (ampere metre2) B = magnetic field induction (tesla)  = angle between the direction of the dipole axis and the magnetic field (degrees) Potential energy of a dipole in a magnetic field U  MB(cos 2  cos 1 )  = torque (newton metre) U = potential energy (joule) 1 .com 2 .PHYSICS MAGNETISM AND MATTER Magnetism and Matter Top Formulae Formula Magnetic dipole moment Description M = magnetic dipole moment (ampere metre2) M  m2l m = pole strength (ampere metre) 2l = magnetic length (metre) Force between two magnetic  2m1m2 poles F  0 4 r2 Magnetic field strength at a point on the axial line of a bar magnet  2Md B1  0 2 2 2 4 (d  l )  2M when l2  d2 . 2 = angles (degrees) M = magnetic dipole moment (ampere metre2) www.B1  0 3 4 d Magnetic field strength at a point on the equatorial line of a bar magnet  M B2  0 2 2 3 / 2 4 (d  l )  M when l2  d2 .topperlearning. com B = magnetic field induction (tesla) H = magnetic field intensity (ampere metre−1) m = magnetic susceptibility I =magnetic moment/volume (ampere metre−1) 3 .topperlearning. the apparent value of the angle of dip Z ZE tanI tanI'  E   HE ' HE cos  cos  HE = horizontal component (tesla) ZE = vertical component (tesla) BE = resultant field of the Earth (tesla) I = angle of dip (degrees) HE = horizontal component (tesla) HE′ = horizontal component in the direction of the magnetic needle (tesla) ZE = vertical component (tesla) I = angle of dip (degrees) I′ = apparent value of the angle of dip (degrees) Tangent law F  Htan   = angle through which magnetic needle is turned (degrees) F = field intensity (tesla) H = field intensity (tesla)  = angle with H (degrees) Magnetic moment of an atom due to revolving of an electron eh M  n( )  nB 4m eh where B  4m M = magnetic moment (ampere metre2) B = Bohr magneton (ampere metre2) n = number of orbit m = mass of electron (kg) h = Planck’s constant (joule second) e = charge of electron (coulomb)  = permeability (tesla ampere−1)  B H I H  r  0 B  0 (H  I) m  r  1  m www.PHYSICS MAGNETISM AND MATTER B = magnetic field induction (tesla) Declination D = angle between magnetic meridian and geographic meridian Magnetic elements of the Earth HE  BE cos I ZE  BE sinI BE  HE2  ZE2 tanI  ZE HE When the vertical plane carrying the magnetic needle is turned through angle  . S  0 all area elements S  The pole near the geographic North Pole of the Earth is called the north magnetic pole. Like magnetic poles repel and unlike poles attract each other.    B. Cutting a bar magnet in two leads to two smaller magnets. where we choose the zero of the energy at the orientation when m is perpendicular to B .m.  Three quantities are needed to specify the magnetic field of the Earth on its surface—the horizontal component. The pole near the geographic South Pole is called the south magnetic pole. The magnitude of the magnetic field on the Earth’s surface = 4 × 10−5 T. the magnetic field B due to this bar is B µ0 m 2πr3   µ0 m 4πr3  along axis   along equator  Gauss’s law for magnetism: The net magnetic flux through any closed surface is zero. the magnetic declination and the magnetic dip. o The torque on it is m x B . www.com 4 . These are known as the elements of the Earth’s magnetic field. o Its potential energy is .PHYSICS MAGNETISM AND MATTER r = relative permeability 0 = permeability of free space (tesla ampere−1) m = magnetic susceptibility Curie law C m  T C = constant T = temperature (°K) Top Concepts  Magnetic materials tend to point in the north–south direction.topperlearning. o The force on it is zero.  When a bar magnet of dipole moment m is placed in a uniform magnetic field B .  Consider a bar magnet of size and magnetic moment m at a distance r from its midpoint where r >> . B . Magnetic poles cannot be isolated.  is negative and small. B  µr H where  : Magnetic susceptibility of the material µr: Relative magnetic permeability The relative magnetic permeability µr and the magnetic permeability  are related as follows: µ = µ0 µr µr = 1 +   Magnetic materials are broadly classified as diamagnetic. The magnetic field B in the material is   B  µ0 H  M  For a linear material M   H . paramagnetic and ferromagnetic. For paramagnetic materials. So. The magnetic intensity is defined as H B0 µ0 The magnetisation M of the material is its dipole moment per unit volume.  is positive and small. www.topperlearning.PHYSICS MAGNETISM AND MATTER  Consider a material placed in an external magnetic field B0 .  is positive and large. For diamagnetic materials. For ferromagnetic materials.com 5 .  Substances which at room temperature retain their ferromagnetic property for a long period of time are called permanent magnets.