Download Dielectric Properties of Materials

Physics Tutorial Sheet
Dielectric Properties of Materials
1) Explain the behavior of dielectrics under static electric fields. Derive a

Physics Tutorial Sheet
Dielectric Properties of Materials
1) Explain the behavior of dielectrics under static electric fields. Derive a

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relation between P and E .
2) Explain the different types of polarization mechanism in dielectrics.
3) What is local field? Obtain an expression for Lorentz equation for local
field and hence deduce Clausius-Mossotti relation.
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4) Give the relationship between i) E , D and P vectors ii) dielectric
4) Give the relationship between i)
6)
7)
8)
iii) dielectric constant and dielectric
susceptibility. What is the significance of each of these factors?
Derive a relation between dielectric constant and refractive index of
the dielectric.
Explain the phenomenon of spontaneous polarization in ferroelectric
materials. Give important applications of ferroelectricity.
What is piezoelectricity? Discuss direct and inverse piezoelectric
effects. Explain their importance and applications.
What is dielectric loss? Show that dielectric loss is given by the

9)
10)
11)
12)
13)
14)
15)
16)
n
r
5)
6)
7)
8)
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constant and vector P iii) dielectric constant and dielectric
susceptibility. What is the significance of each of these factors?
Derive a relation between dielectric constant and refractive index of
the dielectric.
Explain the phenomenon of spontaneous polarization in ferroelectric
materials. Give important applications of ferroelectricity.
What is piezoelectricity? Discuss direct and inverse piezoelectric
effects. Explain their importance and applications.
What is dielectric loss? Show that dielectric loss is given by the
 rn

r .
relation, tan  =
Explain frequency dependence of dielectric constant.
Find polarization (P) in dielectric material with dielectric constant, r =
2.8, when D = 3 × 10-8C/m2.
An electric field of 6 × 104 volt/meter is applied on a sample of Neon
gas at N.T.P. Calculate the dipole moment induced if the dielectric
constant of Neon at N.T.P. is 1.000134. Also find out the atomic
polarizability of Neon.
The permittivity of diamond is 1.46 × 10-10 N-1m-2. Determine its
dielectric constant and electrical susceptibility. (Given 0 = 8.86 × 1012 C2N-1m-2).
The number of atoms in volume of one cubic meter of hydrogen gas is
9.8 × 1026. The radius of the hydrogen atom is 0.53 Å. Calculate the
polarizability and relative permittivity.
The following data refers to a dielectric material; r = 4.94 and n2 =
2.69, where n is the index of refraction, calculate the ratio between
electronic and ionic polarizability for this material.
Calculate the frequency of the fundamental note emitted by a quartz
crystal. Given thickness of quartz crystal plate = 5.5 × 10-3m, Young’s
modulus of Quartz = 8 × 10-10m-2 and density of the crystal = 2.65 ×
103 kg m-3.
For ice, relaxation time is given as 18 × 10-6 sec at 22°C. Calculate
the frequency when the real and imaginary parts of the complex
dielectric constant will become equal. What will be the phase
difference between the current and voltage at this frequency? Which of
the two will be leading in phase?

E , D and P vectors ii) dielectric


constant and vector P
5)

relation between P and E .
2) Explain the different types of polarization mechanism in dielectrics.
3) What is local field? Obtain an expression for Lorentz equation for local
field and hence deduce Clausius-Mossotti relation.
9)
10)
11)
12)
13)
14)
15)
16)

r .
relation, tan  =
Explain frequency dependence of dielectric constant.
Find polarization (P) in dielectric material with dielectric constant, r =
2.8, when D = 3 × 10-8C/m2.
An electric field of 6 × 104 volt/meter is applied on a sample of Neon
gas at N.T.P. Calculate the dipole moment induced if the dielectric
constant of Neon at N.T.P. is 1.000134. Also find out the atomic
polarizability of Neon.
The permittivity of diamond is 1.46 × 10-10 N-1m-2. Determine its
dielectric constant and electrical susceptibility. (Given 0 = 8.86 × 1012 C2N-1m-2).
The number of atoms in volume of one cubic meter of hydrogen gas is
9.8 × 1026. The radius of the hydrogen atom is 0.53 Å. Calculate the
polarizability and relative permittivity.
The following data refers to a dielectric material; r = 4.94 and n2 =
2.69, where n is the index of refraction, calculate the ratio between
electronic and ionic polarizability for this material.
Calculate the frequency of the fundamental note emitted by a quartz
crystal. Given thickness of quartz crystal plate = 5.5 × 10-3m, Young’s
modulus of Quartz = 8 × 10-10m-2 and density of the crystal = 2.65 ×
103 kg m-3.
For ice, relaxation time is given as 18 × 10-6 sec at 22°C. Calculate
the frequency when the real and imaginary parts of the complex
dielectric constant will become equal. What will be the phase
difference between the current and voltage at this frequency? Which of
the two will be leading in phase?