Types of Ferrites and Magnetostriction
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Questions and Answers

What is a primary characteristic of soft ferrites?

  • They are used in transformer or electromagnetic cores. (correct)
  • They retain significant magnetization.
  • They are not suitable for household products.
  • They have high coercivity.

    • Which type of ferrite is specifically known for retaining permanent magnetization?

  • Strontium ferrite (correct)
  • Nickel-zinc ferrite
  • Copper-zinc ferrite
  • Manganese-zinc ferrite

    • Who first measured magnetostriction?

  • Albert Einstein
  • Gustav Wiedemann
  • E.Villari
  • James Prescott Joule (correct)

    • What is the effect discovered by E.Villari?

    <p>The oscillation of a ferromagnetic rod under stress.</p> Signup and view all the answers

    Which statement is true about magnetostriction in ferromagnetic materials?

    <p>Ferromagnetic materials that are isotropic are more effective in magnetostriction.</p> Signup and view all the answers

    What is the process called when an excited electron interacts with a photon and decays to a lower energy level?

    <p>Stimulated emission</p> Signup and view all the answers

    Laser light is characterized by having many different wavelengths.

    <p>False</p> Signup and view all the answers

    Name one of the four characteristics that differentiate laser light from ordinary light.

    <p>Coherence</p> Signup and view all the answers

    In lasers, electron transition occurs in a specific _____ resulting in coherent light.

    <p>time</p> Signup and view all the answers

    Match the characteristic of laser light with its description:

    <p>Coherence = Same phase and frequency Directionality = Converging into a narrow beam Monochromatic = Single wavelength of light High intensity = Greater power concentration</p> Signup and view all the answers

    Which characteristic of laser light enables it to concentrate power in a narrow space?

    <p>Coherence</p> Signup and view all the answers

    Photons emitted from ordinary light sources travel in a directed manner.

    <p>False</p> Signup and view all the answers

    What happens to the energy of the excited electron during stimulated emission?

    <p>It is converted to the energy of a photon.</p> Signup and view all the answers

    What is the main role of active centers in active mediums?

    <p>To produce more stimulated emission than spontaneous emission</p> Signup and view all the answers

    The function of a resonance cavity is to accommodate the active medium and to reflect light.

    <p>True</p> Signup and view all the answers

    What is the typical loss percentage introduced by fibre optic connectors at each connection?

    <p>10 to 20 percent</p> Signup and view all the answers

    Fibre optic connectors are required for connecting a fibre optic cable to another _____ or an electronic interface device.

    <p>cable</p> Signup and view all the answers

    What is the purpose of polishing fibre ends?

    <p>To achieve physical contact between two connectors</p> Signup and view all the answers

    Match the following components with their descriptions:

    <p>Active Medium = Contains atoms that produce stimulated emission Energy Source = Pumps active centers to achieve population inversion Resonance Cavity = Encloses the active medium and includes mirrors Fibre Optic Connector = Used to interface fibre optic cables with minimized light loss</p> Signup and view all the answers

    Fibre optic connectors should be used as frequently as possible to prevent light loss.

    <p>False</p> Signup and view all the answers

    What is the significance of the connectors holding the fibre optic cable accurately in place?

    <p>To ensure maximum light transfer occurs</p> Signup and view all the answers

    Which of the following best describes monochromatic light?

    <p>Light containing a single color or wavelength</p> Signup and view all the answers

    The diameter of a laser beam can spread to more than 2 km when traveling a distance of 2 km.

    <p>False</p> Signup and view all the answers

    What property of laser light allows it to travel long distances without spreading?

    <p>Directionality</p> Signup and view all the answers

    Ordinary light is a mixture of waves having different frequencies or __________.

    <p>wavelengths</p> Signup and view all the answers

    Match the properties of laser light with their characteristics:

    <p>Directionality = Emits light in all directions Monochromatic = Contains a single wavelength Intensity = Energy per unit area increases Polarization = Behavior in an electric field differs from conductors</p> Signup and view all the answers

    What happens to the intensity of a laser compared to an ordinary light source?

    <p>It is greater than ordinary light</p> Signup and view all the answers

    Dielectrics are materials that conduct electric current well.

    <p>False</p> Signup and view all the answers

    What is a characteristic behavior of dielectrics in an electric field?

    <p>They can be easily polarized.</p> Signup and view all the answers

    What type of materials are characterized by no net magnetic moments and are typically weakly magnetic?

    <p>Diamagnetic materials</p> Signup and view all the answers

    Paramagnetic materials are strongly attracted to a magnet.

    <p>False</p> Signup and view all the answers

    Which materials have individual atomic dipoles that orient themselves parallel to an applied magnetic field?

    <p>Paramagnetic materials</p> Signup and view all the answers

    Diamagnetic materials exhibit a __________ susceptibility.

    <p>negative</p> Signup and view all the answers

    Match the following materials with their characteristics:

    <p>Diamagnetic materials = No permanent magnetic dipoles Paramagnetic materials = Require a strong external magnetic field Ferromagnetic materials = Strongly attracted to magnets Aluminium = Examples of paramagnetic materials</p> Signup and view all the answers

    Which of the following is NOT a characteristic of ferromagnetic materials?

    <p>Absent orientation of magnetic dipoles</p> Signup and view all the answers

    All matter exhibits diamagnetism.

    <p>True</p> Signup and view all the answers

    The permeability of aluminium is __________.

    <p>1.00000065</p> Signup and view all the answers

    What happens to the dipole moment of a non-polar molecule when placed in an electric field?

    <p>It gets induced along the electric field.</p> Signup and view all the answers

    The induced electric dipole moment in a non-polar molecule depends on temperature.

    <p>False</p> Signup and view all the answers

    Define polarization in the context of molecules placed in an electric field.

    <p>Polarization is the alignment of dipole moments of molecules with the direction of the applied electric field.</p> Signup and view all the answers

    In CO2, the net dipole moment is _____ when the molecule is symmetrical.

    <p>zero</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Induced dipole moment = Moment created when an external electric field is applied to a non-polar molecule Polar molecule = Molecule that has a permanent dipole moment Dielectric polarization = Alignment of dipole moments in a dielectric under an electric field Electric field = A field produced by charged particles that exerts force on other charged particles</p> Signup and view all the answers

    When the electric field is removed, what happens to the induced dipole moment?

    <p>It disappears.</p> Signup and view all the answers

    The positive charges in a dielectric slab move in the opposite direction of the electric field.

    <p>False</p> Signup and view all the answers

    What is the primary factor that differentiates polar molecules from non-polar molecules regarding dipole moments?

    <p>Temperature dependence of dipole moment in polar molecules.</p> Signup and view all the answers

    What happens during spontaneous emission?

    <p>An excited electron decays to a lower energy level and emits a photon.</p> Signup and view all the answers

    Spontaneous emission requires interaction with other photons.

    <p>False</p> Signup and view all the answers

    What is the average time for decay by spontaneous emission called?

    <p>spontaneous emission lifetime</p> Signup and view all the answers

    If spontaneous emission occurs due to a chemical reaction, it is known as ______.

    <p>chemiluminescence</p> Signup and view all the answers

    Which process is described when glow sticks produce light?

    <p>Chemiluminescence</p> Signup and view all the answers

    Match the following processes of spontaneous emission with their respective energy sources:

    <p>Photoluminescence = Optical energy Chemiluminescence = Chemical reaction Electroluminescence = Voltage Bioluminescence = Living organism</p> Signup and view all the answers

    What is the process called when an electron absorbs a photon and moves to a higher energy level?

    <p>absorption</p> Signup and view all the answers

    The energy of the emitted photon during spontaneous emission is independent of the energy levels involved.

    <p>False</p> Signup and view all the answers

    Study Notes

    Types of Ferrites

    • Ferrites are classified as soft or hard based on magnetic properties.
    • Soft ferrites have low coercivity and are used in transformer or electromagnetic cores (e.g., manganese-zinc ferrite, nickel-zinc ferrite).
    • Hard ferrites have high coercivity, are inexpensive, and commonly used in household products like refrigerator magnets (e.g., strontium ferrite, barium ferrite).
    • Soft ferrites do not retain significant magnetization, while hard ferrite magnetization is considered permanent.

    Magnetostriction

    • As the applied magnetic field increases, magnetostrictive strain on the material increases.
    • Isotropic ferromagnetic materials with low impurities are most effective in magnetostriction because their molecular dipoles rotate easily.
    • James Prescott Joule measured magnetostriction by magnetizing an iron sample and measuring the change in length.
    • E. Villari discovered the opposite effect, where applied stress creates a magnetic field.
    • Gustav Wiedemann discovered that a ferromagnetic rod oscillates torsionally when exposed to longitudinal and circular magnetic fields.

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    Description

    This quiz covers the classification of ferrites into soft and hard types based on their magnetic properties. It also explores the concept of magnetostriction and its significance in ferromagnetic materials. Test your understanding of these important concepts in magnetism.

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