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#magnetism basics

3 public questions tagged with this topic.

Magnetization, Magnetic Intensity, Susceptibility and Permeability

The magnetic field lines inside a bar magnet run from:

**Magnetic properties** μ_r = 400 indicates 400 times vacuum permeability, so B enhanced 400 times for same nI. H = nI (A/m) for solenoid, M = χ H, B = μ₀(H+M) links microscopic magnetization to macroscopic field. Magnetic field lines form closed loops, exiting the north pole and entering the south pole externally. Inside a bar magnet, they run from the south pole to the north pole to complete the loop, consistent with the convention of field direction from north to south outside. Substituting values gives South to north, which matches expected magnitude for this magnetic configuration, confirming dipole field dependence on m/r³ and torque

Ref: NCERT > Physics Book > Magnetism and Matter > Magnetization, Magnetic Intensity, Susceptibility and Permeability

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Magnetization, Magnetic Intensity, Susceptibility and Permeability

A material with \( \chi = -1 \) and \( \mu_r = 0 \) is classified as:

**Magnetization M** is magnetic moment per unit volume (A/m), magnetic intensity H = B/μ₀ - M, susceptibility χ = M/H dimensionless, permeability μ = B/H = μ₀(1+χ), relative permeability μ_r = μ/μ₀ = 1+χ. For solenoid with core, B = μ₀ μ_r n I, n turns per meter (m⁻¹), I current (A). A material with chi = -1 and μ_r = 0 exhibits perfect diamagnetism, characteristic of a superconductor due to the Meissner effect. Substituting values gives Superconductor, which matches expected magnitude for this magnetic configuration, confirming dipole field dependence on m/r³ and torque relation τ = m B sinθ.

Ref: NCERT > Physics Book > Magnetism and Matter > Magnetization, Magnetic Intensity, Susceptibility and Permeability

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Magnetic Field Lines, Bar Magnet and Dipole Moment

A material that weakly repels magnetic field lines and has a susceptibility slightly less than zero is classified as:

**Magnetic field lines** form continuous closed loops, direction given by tangent at point, density indicates field strength. Unlike electric field lines, magnetic lines never intersect because unique field direction exists at each point, and bar magnet possesses dipole moment m = N I A directed from south to north pole inside magnet. Diamagnetic materials have a small negative susceptibility ( chi < 0 ), causing them to weakly repel magnetic field lines. This occurs because an applied magnetic field induces an opposing magnetic moment in the material, reducing the field inside it. Substituting values gives Diamagnetic, which matches expected magnitude for this magnetic configuration, confirming

Ref: NCERT > Physics Book > Magnetism and Matter > Magnetic Field Lines, Bar Magnet and Dipole Moment

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