Magnetic susceptibility ( \( \chi \) ) measures how much a material becomes magnetized when placed in an external magnetic field.
Magnetic permeability ( \( \mu \) ) represents how easily magnetic field lines can pass through a material.
Discuss the origin of magnetic moment in an atom.
Magnetic moment in an atom arises from the orbital motion of electrons, their spin angular momentum, and the nuclear magnetic moment (usually very small).
State Weiss’s domain theory of ferromagnetism.
A ferromagnetic material contains many small regions called domains, each with spontaneous magnetization.
In an unmagnetized sample, domains are randomly oriented, resulting in zero net magnetization.
Write two differences between soft and hard magnetic materials.
Soft magnetic materials have low coercivity and are easy to magnetize and demagnetize.
Hard magnetic materials have high coercivity and retain magnetization permanently.
Why are permanent magnets important in electric vehicles?
Permanent magnets provide strong and stable magnetic fields required for high-efficiency motors, improving power density and energy efficiency in electric vehicles.
Why does orientation polarization vanish at high temperatures?
At high temperatures, thermal agitation randomizes dipole orientations, preventing alignment with the applied electric field.
Illustrate how spontaneous magnetization occurs in a ferromagnetic material without an external field.
Strong exchange interactions cause atomic magnetic moments to align parallel within domains, producing spontaneous magnetization even in the absence of an external field.
Explain the meaning of coercivity in a magnetic material.
Coercivity is the magnitude of the reverse magnetic field required to reduce the magnetization of a material to zero after saturation.
Write two applications of ferroelectric materials.
Ferroelectric materials are used in non-volatile memory devices (FeRAM) and in sensors and actuators due to their large polarization changes.
Which type of polarization is temperature dependent?
Orientation polarization is strongly temperature dependent because dipolar alignment decreases with increasing temperature.
Explain why ferroelectrics are used in Fe-RAM.
Ferroelectrics possess two stable polarization states that can represent binary data, enabling fast, low-power, non-volatile memory storage.
Give one example each of soft and hard magnetic materials.
Soft magnetic materials include silicon steel and permalloy.
Hard magnetic materials include NdFeB (neodymium magnets) and Alnico.
Why are soft magnetic materials suitable for electrical machines?
Soft magnetic materials have low hysteresis loss and allow rapid magnetization and demagnetization, making them suitable for transformers and motors.
Explain why the given material is classified as a magnetic.
A magnetic does not conduct electricity but becomes polarized in an electric field, storing electrical energy rather than allowing charge flow.
Which sensor uses pyroelectric materials?
Passive Infrared (PIR) sensors use pyroelectric materials to detect changes in infrared radiation and are widely used in motion detection systems.