### Electronics & Electrical Mcqs

Q:

Solids do not have which type of polarisation?

 A) Ionic B) Orientational C) Interfacial D) Electronic

Explanation: Solids possess permanent dipole moments. Moreover they do not have junction like semiconductors. Thus, solids neglect the interfacial and space charge polarisation. They possess only electronic, ionic and orientational polarisations.

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Q:

In the given types of polarisation, which type exists in the semiconductor?

 A) Electronic B) Ionic C) Orientational D) Interfacial or space charge

Explanation: The interfacial type of polarisation occurs due to accumulation of charges at the interface in a multiphase material. This interface or junction is found in a semiconductor material.

2
Q:

The total polarisation of a material is the

 A) Product of all types of polarisation B) Sum of all types of polarisation C) Orientation directions of the dipoles D) Total dipole moments in the material

Explanation: The total polarisation of a material is given by the sum of electronic, ionic, orientational and interfacial polarisation of the material.

3
Q:

In isotropic materials, which of the following quantities will be independent of the direction?

 A) Permittivity B) Permeability C) Polarisation D) Polarizability

Explanation: Isotropic materials are those with radiate or absorb energy uniformly in all directions (eg. Isotropic antenna). Thus it is independent of the direction.

3
Q:

Calculate the polarisation vector in air when the susceptibility is 5 and electric field is 12 units.

 A) 3 B) 2 C) 60 D) 2.4

Explanation: The polarisation vector is given by, P = ε0 x χe x E, where χe = 5 and ε0 = 12. On substituting, we get P = 1 x 5 x 12 = 60 units.

3
Q:

Identify which type of polarisation depends on temperature.

 A) Electronic B) Ionic C) Orientational D) Interfacial

Explanation: The electronic, ionic and interfacial polarisation depends on the atoms which are independent with respect to temperature. Only the orientational polarisation is dependent on the temperature and is inversely proportional to it.

2
Q:

Calculate the energy stored per unit volume in a dielectric medium due to polarisation when P = 9 units and E = 8 units.

 A) 1.77 B) 2.25 C) 36 D) 144

Explanation: The energy stored per unit volume in a dielectric medium is given by, W = 0.5 X PE = 0.5 X 9 X 8 = 36 units.

2
Q:

Polarizability is defined as the

 A) Product of dipole moment and electric field B) Ratio of dipole moment to electric field C) Ratio of electric field to dipole moment D) Product of dielectric constant and dipole moment

Answer & Explanation Answer: B) Ratio of dipole moment to electric field

Explanation: Polarizability is a constant that is defined as the ratio of elemental dipole moment to the electric field strength.

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