Dielectric materials week 6 Flashcards
What is a dielectric material?
A dielectric material is an insulating substance that can be polarized by an electric field.
True or False: Dielectric materials conduct electricity.
False
Fill in the blank: The ability of a dielectric material to store electrical energy is characterized by its ______.
permittivity
What is the unit of permittivity?
Farads per meter (F/m)
What is the dielectric constant?
The dielectric constant is the ratio of the permittivity of a material to the permittivity of free space.
List one common application of dielectric materials.
Capacitors
True or False: Dielectric strength is the maximum electric field a dielectric material can withstand without breakdown.
True
What is the relationship between dielectric materials and capacitance?
Dielectric materials increase the capacitance of capacitors by reducing the electric field within the capacitor.
Multiple Choice: Which of the following is NOT a dielectric material? A) Glass B) Water C) Copper D) Teflon
C) Copper
What happens to a dielectric material when exposed to an electric field?
It becomes polarized, meaning that the positive and negative charges within the material are displaced.
Fill in the blank: The process of polarization in dielectric materials involves the alignment of ______ within the material.
dipoles
What is the effect of temperature on the dielectric properties of materials?
Temperature can affect the permittivity and dielectric strength, often decreasing the dielectric strength at higher temperatures.
True or False: All dielectric materials have the same dielectric constant.
False
What is the term for the failure of a dielectric material to insulate against electric stress (subjected to a high electric field)
Dielectric breakdown
Multiple Choice: Which material typically has a high dielectric constant? A) Air B) Rubber C) Water D) Wood
C) Water
What is dielectric loss?
Dielectric loss represents the energy lost as heat in a dielectric material when it is subjected to an alternating electric field.
Fill in the blank: Dielectric materials are often used in ______ to store electrical energy.
capacitors
What is the primary function of a dielectric in a capacitor?
To increase capacitance and store electric charge.
True or False: The dielectric properties of materials can change with frequency.
True
What does the term ‘relative permittivity’ refer to?
It refers to the dielectric constant of a material relative to the permittivity of free space.
Multiple Choice: Which of the following is a characteristic of a good dielectric material? A) High conductivity B) Low dielectric loss C) Low permittivity D) High temperature coefficient
B) Low dielectric loss
What is the role of dielectric materials in insulators?
They prevent the flow of electric current and protect conductors from electrical leakage.
What happens to the capacitance of a capacitor if a dielectric material is inserted?
The capacitance increases.
Fill in the blank: The measure of a material’s ability to resist electric field is known as ______.
dielectric strength
True or False: A higher dielectric constant means a material is a better insulator.
False
What is a ferroelectric material?
A ferroelectric material is a dielectric material that exhibits spontaneous electric polarization that can be reversed by the application of an external electric field.
True or False: All ferroelectrics are also piezoelectric.
True.
Fill in the blank: The property of generating an electric charge in response to mechanical stress is known as __________.
piezoelectricity.
Which of the following is a common application of pyroelectric materials? (A) Energy storage (B) Sensors (C) Insulation
B) Sensors.
What distinguishes pyro- and piezoelectric materials from other dielectric materials?
Pyro- and piezoelectric materials can generate an electric charge in response to temperature changes and mechanical stress, respectively.
What is the ideal electrical conductivity of dielectric materials?
Zero dc electrical conductivity
How is capacitance defined in a parallel plate capacitor with a vacuum?
C0 = e0A/d, where e0 is the permittivity of free space
What is the defining characteristic of non-polar dielectrics?
Centrosymmetric crystal structures
What happens to dielectric materials at high frequencies regarding pliability?
Electronic polarisability dominates
Define the Clausius-Mossotti relation.
It links permittivity and polarisability of a material
What is a polar dielectric?
A dielectric with a dipole moment that can be modified in an electric field
How do piezoelectric materials generate electrical energy?
By mechanical stress applied to them
What does the term ‘hysteresis loop’ refer to in dielectric materials?
The relationship between electric field strength and polarisation
What characteristic distinguishes ferroelectric materials from non-ferroelectric ones?
Ferroelectric materials can change dipole orientation in an electric field
What happens to the dielectric permittivity when the temperature changes in pyroelectric materials?
It becomes temperature-dependent
Which dielectric property describes how the capacitance of a material increases in the presence of an applied electric field?
Which dielectric property describes how the capacitance of a material increases in the presence of an applied electric field?
What kind of structure do antiferroelectric materials have?
Adjacent dipoles arranged antiparallel, leading to zero net polarisation
What is a primary application of piezoelectric materials?
In sensors and actuators
What type of dielectrics can exhibit an anomalous increase in resistivity with temperature?
Certain ferroelectric materials, especially near phase transitions
