UNIT-3 magnetic materials

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What is a magnetic field?

The region around a magnet where it exerts forces on other magnets or magnetic materials.

What defines a magnetic dipole?

A pair of magnetic poles of equal and opposite strengths separated by a finite distance.

How is magnetic flux defined?

The number of magnetic field lines passing through a given surface area.

What is the formula for magnetic induction (B)?

B = Φ/A where Φ is the magnetic flux and A is the area.

What does magnetic field intensity (H) represent?

The force experienced by a unit north pole placed at a point in the magnetic field.

What is the relationship between magnetic flux density (B) and magnetic field intensity (H)?

B = μH, where μ is the permeability of the medium.

What is intensity of magnetization (I)?

The magnetic moment per unit volume of a material.

What is magnetic susceptibility (χ)?

The ratio of the intensity of magnetization produced in the material to the magnetic field intensity that produces it.

What arises from the orbital magnetic moments of electrons?

Permanent magnetic moments in atoms.

What is the Bohr magneton?

A physical constant used to describe the magnetic moment of an electron due to its angular momentum.

How do diamagnetic materials behave in an external magnetic field?

They exhibit weak repulsion and have a negative magnetic susceptibility.

What characterizes paramagnetic materials?

They have permanent magnetic dipoles and exhibit positive magnetic susceptibility.

What is the defining property of ferromagnetic materials?

They exhibit spontaneous magnetization, even in the absence of an external magnetic field.

How does hysteresis relate to ferromagnetic materials?

It refers to the lag of magnetization behind the magnetizing field, showing irreversible processes in domain alignment.

What are soft magnetic materials?

Materials that can be easily magnetized and have low coercivity.

Define antiferromagnetism.

A phenomenon where adjacent magnetic moments point in opposite directions, resulting in zero net magnetization.

What occurs at the Neel temperature in antiferromagnetic materials?

The spin ordering is lost completely, transitioning to paramagnetic behavior.

What are ferrimagnetic materials?

Materials where two sublattices have unequal magnetic moments that are oriented in opposite directions, resulting in a net magnetization.

What is the Meissner effect?

The phenomenon where a superconductor expels magnetic flux from its interior when cooled below its critical temperature.

What distinguishes Type I superconductors from Type II superconductors?

Type I superconductors exhibit perfect diamagnetism, while Type II allows magnetic flux penetration at certain field strengths.

What application is enabled by the superconducting characteristic of zero electrical resistance?

Low loss transmission lines and transformers for efficient power delivery.

What happens to superconductors when exposed to a strong magnetic field beyond the critical magnetic field?

They transition from the superconducting state to the normal state.