Electric Fields In Material Space - Questions With Answers (Short Notes)
01. How Can Materials Be Classified In Terms Of Their Electrical Properties?
Answer: Materials can be classified roughly as conductors (σ >> 1, εr = 1) and dielectrics (σ << 1, εr ≥ 1) in terms of their electrical properties σ and εr where σ is the conductivity and εr is the dielectric constant or relative permittivity.
A material with high conductivity ( σ >> 1) is referred to as a metal whereas one with low conductivity (σ << 1) is referred to as an insulator. A material whose conductivity lies somewhere between those of metals and insulators is called a semiconductor.
02. Define Superconductor?
Answer: The conductivity of metals generally increases with decrease in temperature. At temperatures near absolute zero (T = 0°K), some conductors exhibit infinite conductivity and are called superconductors. Lead and aluminum are typical examples of such metals.
03. Why Conductor Is Called An Equipotential Body? What Are Perfect Conductors?
Answer: A conductor is called an equipotential body, implying that the potential is the same everywhere in the conductor. This is based on the fact that E = -∇V = 0.
A perfect conductor is one which cannot contain an electrostatic field within it.
04. What Is Electric Susceptibility Of The Material?
Answer: Electric susceptibility of the material, is more or less a measure of how susceptible (or sensitive) a given dielectric is to electric fields.
Electric susceptibility (χe) is a material property that measures the extent of polarization in the material per unit field, i.e., χe = P/E. It relates the amount of polarization, P at a point in the dielectric to the field, E at that point via P = χeE = ε0(εr-1)E, here ε0 is the permittivity of free space and εr is the relative permittivity.
In simple words, The electric susceptibility χe of a dielectric measures the sensitivity of the material to an electric field.
05. What Is Dielectric Constant Or Relative Permittivity?
Answer: The dielectric constant (or relative permittivity) εr, is the ratio of the permittivity
of the dielectric to that of free space.
ε is called the permittivity of the dielectric, ε0 is the permittivity of free space and εr is called the dielectric constant or relative permittivity.
06. What Is Dielectric Strength? When Does A Dielectric Breakdown Occur?
Answer: The dielectric strength is the maximum electric field that a dielectric can tolerate or withstand without breakdown.
Dielectric breakdown occurs when a dielectric becomes conducting. Dielectric breakdown occurs in all kinds of dielectric materials (gases, liquids, or solids) and depends on the nature of the material, temperature, humidity, and the amount of time that the field is applied. The minimum value of the electric field at which dielectric breakdown occurs is called the dielectric strength of the dielectric material.
07. What Are Linear, Isotropic & Homogeneous Dielectrics?
Answer: A dielectric material (in which D = εE applies) is linear if ε does not change with the applied E field, homogeneous if ε does not change from point lo point, and isotropic if ε does not change with direction.
08. In A Dielectric Medium, How Are D & E Related. When A Dielectric Material Is Said To Be Linear, Isotropic & Homogeneous?
Answer: In a dielectric medium, the D and E fields are related as D = εE, where ε = ε0εr is the permittivity of the medium.
A dielectric material is linear if D = εE holds, that is, if ε is independent of E. It is homogeneous if ε is independent of position. It is isotropic if ε is a scalar.
Answer: Materials can be classified roughly as conductors (σ >> 1, εr = 1) and dielectrics (σ << 1, εr ≥ 1) in terms of their electrical properties σ and εr where σ is the conductivity and εr is the dielectric constant or relative permittivity.
A material with high conductivity ( σ >> 1) is referred to as a metal whereas one with low conductivity (σ << 1) is referred to as an insulator. A material whose conductivity lies somewhere between those of metals and insulators is called a semiconductor.
02. Define Superconductor?
Answer: The conductivity of metals generally increases with decrease in temperature. At temperatures near absolute zero (T = 0°K), some conductors exhibit infinite conductivity and are called superconductors. Lead and aluminum are typical examples of such metals.
03. Why Conductor Is Called An Equipotential Body? What Are Perfect Conductors?
Answer: A conductor is called an equipotential body, implying that the potential is the same everywhere in the conductor. This is based on the fact that E = -∇V = 0.
A perfect conductor is one which cannot contain an electrostatic field within it.
04. What Is Electric Susceptibility Of The Material?
Answer: Electric susceptibility of the material, is more or less a measure of how susceptible (or sensitive) a given dielectric is to electric fields.
Electric susceptibility (χe) is a material property that measures the extent of polarization in the material per unit field, i.e., χe = P/E. It relates the amount of polarization, P at a point in the dielectric to the field, E at that point via P = χeE = ε0(εr-1)E, here ε0 is the permittivity of free space and εr is the relative permittivity.
In simple words, The electric susceptibility χe of a dielectric measures the sensitivity of the material to an electric field.
05. What Is Dielectric Constant Or Relative Permittivity?
Answer: The dielectric constant (or relative permittivity) εr, is the ratio of the permittivity
of the dielectric to that of free space.
εr = ε / ε0
ε is called the permittivity of the dielectric, ε0 is the permittivity of free space and εr is called the dielectric constant or relative permittivity.
06. What Is Dielectric Strength? When Does A Dielectric Breakdown Occur?
Answer: The dielectric strength is the maximum electric field that a dielectric can tolerate or withstand without breakdown.
Dielectric breakdown occurs when a dielectric becomes conducting. Dielectric breakdown occurs in all kinds of dielectric materials (gases, liquids, or solids) and depends on the nature of the material, temperature, humidity, and the amount of time that the field is applied. The minimum value of the electric field at which dielectric breakdown occurs is called the dielectric strength of the dielectric material.
07. What Are Linear, Isotropic & Homogeneous Dielectrics?
Answer: A dielectric material (in which D = εE applies) is linear if ε does not change with the applied E field, homogeneous if ε does not change from point lo point, and isotropic if ε does not change with direction.
08. In A Dielectric Medium, How Are D & E Related. When A Dielectric Material Is Said To Be Linear, Isotropic & Homogeneous?
Answer: In a dielectric medium, the D and E fields are related as D = εE, where ε = ε0εr is the permittivity of the medium.
A dielectric material is linear if D = εE holds, that is, if ε is independent of E. It is homogeneous if ε is independent of position. It is isotropic if ε is a scalar.
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