Physics · Class 12 · Chapter 5
Magnetism and Matter
11 lessons 81 min 2 simulations
This chapter treats magnetism as a subject of its own. It starts from the bar magnet: its field lines, why it behaves like a solenoid, the torque and energy of a magnetic dipole in a uniform field and the dipole's far field, borrowed from the electric dipole. Gauss's law for magnetism records that there are no magnetic monopoles. The second half describes matter in a field through magnetisation M, magnetic intensity H, susceptibility χ and permeability μ, and sorts materials into diamagnetic, paramagnetic and ferromagnetic.
What the exam asks
NEET asks for the torque mB sin θ and the energy −mB cos θ of a magnet in a field, the work to turn it, and the axial and equatorial fields at a distance. The material half is mostly classification: the sign and size of χ and μr for dia-, para- and ferromagnets, examples of each, B = μ₀(H + M) and M = χH. Marks are lost on the zero of potential energy, on the sign of the equatorial field, and on mixing up which materials are pushed out of a strong field.
Lessons
11 lessons · 81 min
1Magnets and their polesNCERT §5.15 min2Magnetic field linesNCERT §5.2, §5.2.16 min3Bar magnet as an equivalent solenoidNCERT §5.2.25 min4Dipole in a uniform fieldNCERT §5.2.310 min 1 sim5The electrostatic analogNCERT §5.2.46 min6Gauss's law for magnetismNCERT §5.36 min7Magnetisation and magnetic intensityNCERT §5.410 min 1 sim8DiamagnetismNCERT §5.5, §5.5.16 min9ParamagnetismNCERT §5.5.26 min10FerromagnetismNCERT §5.5.36 min11Chapter reviewMust-know facts, traps and formulas15 min