Dielectric materials week 6

Question 1

What is a dielectric material?

Answer 1

A dielectric material is an insulating substance that can be polarized by an electric field.

Question 2

True or False: Dielectric materials conduct electricity.

Answer 2

False

Question 3

Fill in the blank: The ability of a dielectric material to store electrical energy is characterized by its ______.

Answer 3

permittivity

Question 4

What is the unit of permittivity?

Answer 4

Farads per meter (F/m)

Question 5

What is the dielectric constant?

Answer 5

The dielectric constant is the ratio of the permittivity of a material to the permittivity of free space.

Question 6

List one common application of dielectric materials.

Answer 6

Capacitors

Question 7

True or False: Dielectric strength is the maximum electric field a dielectric material can withstand without breakdown.

Answer 7

True

Question 8

What is the relationship between dielectric materials and capacitance?

Answer 8

Dielectric materials increase the capacitance of capacitors by reducing the electric field within the capacitor.

Question 9

Multiple Choice: Which of the following is NOT a dielectric material? A) Glass B) Water C) Copper D) Teflon

Answer 9

C) Copper

Question 10

What happens to a dielectric material when exposed to an electric field?

Answer 10

It becomes polarized, meaning that the positive and negative charges within the material are displaced.

Question 11

Fill in the blank: The process of polarization in dielectric materials involves the alignment of ______ within the material.

Answer 11

dipoles

Question 12

What is the effect of temperature on the dielectric properties of materials?

Answer 12

Temperature can affect the permittivity and dielectric strength, often decreasing the dielectric strength at higher temperatures.

Question 13

True or False: All dielectric materials have the same dielectric constant.

Answer 13

False

Question 14

What is the term for the failure of a dielectric material to insulate against electric stress (subjected to a high electric field)

Answer 14

Dielectric breakdown

Question 15

Multiple Choice: Which material typically has a high dielectric constant? A) Air B) Rubber C) Water D) Wood

Answer 15

C) Water

Question 16

What is dielectric loss?

Answer 16

Dielectric loss represents the energy lost as heat in a dielectric material when it is subjected to an alternating electric field.

Question 17

Fill in the blank: Dielectric materials are often used in ______ to store electrical energy.

Answer 17

capacitors

Question 18

What is the primary function of a dielectric in a capacitor?

Answer 18

To increase capacitance and store electric charge.

Question 19

True or False: The dielectric properties of materials can change with frequency.

Answer 19

True

Question 20

What does the term ‘relative permittivity’ refer to?

Answer 20

It refers to the dielectric constant of a material relative to the permittivity of free space.

Question 21

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

Answer 21

B) Low dielectric loss

Question 22

What is the role of dielectric materials in insulators?

Answer 22

They prevent the flow of electric current and protect conductors from electrical leakage.

Question 23

What happens to the capacitance of a capacitor if a dielectric material is inserted?

Answer 23

The capacitance increases.

Question 24

Fill in the blank: The measure of a material’s ability to resist electric field is known as ______.

Answer 24

dielectric strength

Question 25

True or False: A higher dielectric constant means a material is a better insulator.

Answer 25

False

Question 27

What is a ferroelectric material?

Answer 27

A ferroelectric material is a dielectric material that exhibits spontaneous electric polarization that can be reversed by the application of an external electric field.

Question 28

True or False: All ferroelectrics are also piezoelectric.

Answer 28

True.

Question 29

Fill in the blank: The property of generating an electric charge in response to mechanical stress is known as __________.

Answer 29

piezoelectricity.

Question 30

Which of the following is a common application of pyroelectric materials? (A) Energy storage (B) Sensors (C) Insulation

Answer 30

B) Sensors.

Question 31

What distinguishes pyro- and piezoelectric materials from other dielectric materials?

Answer 31

Pyro- and piezoelectric materials can generate an electric charge in response to temperature changes and mechanical stress, respectively.

Question 32

What is the ideal electrical conductivity of dielectric materials?

Answer 32

Zero dc electrical conductivity

Question 33

How is capacitance defined in a parallel plate capacitor with a vacuum?

Answer 33

C0 = e0A/d, where e0 is the permittivity of free space

Question 34

What is the defining characteristic of non-polar dielectrics?

Answer 34

Centrosymmetric crystal structures

Question 35

What happens to dielectric materials at high frequencies regarding pliability?

Answer 35

Electronic polarisability dominates

Question 36

Define the Clausius-Mossotti relation.

Answer 36

It links permittivity and polarisability of a material

Question 37

What is a polar dielectric?

Answer 37

A dielectric with a dipole moment that can be modified in an electric field

Question 38

How do piezoelectric materials generate electrical energy?

Answer 38

By mechanical stress applied to them

Question 39

What does the term 'hysteresis loop' refer to in dielectric materials?

Answer 39

The relationship between electric field strength and polarisation

Question 40

What characteristic distinguishes ferroelectric materials from non-ferroelectric ones?

Answer 40

Ferroelectric materials can change dipole orientation in an electric field

Question 41

What happens to the dielectric permittivity when the temperature changes in pyroelectric materials?

Answer 41

It becomes temperature-dependent

Question 42

Which dielectric property describes how the capacitance of a material increases in the presence of an applied electric field?

Answer 42

Which dielectric property describes how the capacitance of a material increases in the presence of an applied electric field?

Question 43

What kind of structure do antiferroelectric materials have?

Answer 43

Adjacent dipoles arranged antiparallel, leading to zero net polarisation

Question 44

What is a primary application of piezoelectric materials?

Answer 44

In sensors and actuators

Question 45

What type of dielectrics can exhibit an anomalous increase in resistivity with temperature?

Answer 45

Certain ferroelectric materials, especially near phase transitions