125 + Interview Questions in Materials and Components in electronics and communication engineering Page 3 InterviewSolution

101.	The - relation for an arc is = 44 + . If = 50 V, =
Answer» .

Discussion

102.	The units for intrinsic strength of dielectric are
Answer» Dielectric strength is expressed in volts (or kV) per unit distance (cm or mm).

Discussion

103.	An atom of a rare gas is placed is an electric field E. Then
Answer» For equilibrium nucleus is shifted in the direction of E by an amount which is proportional to E.

Discussion

104.	In van der walls crystals, there exists a high degree of stability of the outer electron shell.
Answer» This is the reason for chemical inactivity in these crystals.

Discussion

105.	In a coaxial cable, braided copper is used for
Answer» Braided material is used for shield.

Discussion

106.	The hysteresis phenomenon in ferromagnetic materials exists at all temperatures.
Answer» Hysteresis phenomenon exists below ferromagnetic curie temperature.

Discussion

107.	If the radius of electron cloud around the nucleus of a rare gas atom is R, the electronic polarizability of the atom is porportional to
Answer» Since (∈r - 1) = 4p NR3, electronic polarizability ∝ R3.

Discussion

108.	By inserting a plate of dielectric between the plates of a parallel plate capacitor, the energy stored in the capacitor is increased five times. The dielectric constant of material is
Answer» Capacitance is directly proportional to dielectric constant.

Discussion

109.	A parallel plate capacitor has its length, width and separation doubled. It fringing effects are neglected, to keep the capacitance same, the dielectric constant must be
Answer» . When dimensions are changed, A become four times and d becomes twice. Since ∈0 is constant, ∈r must be halved to keep C constant.

Discussion

110.	In atomic physics, a state with = 0 is called state.
Answer» The state with l = 0 is called s state.

Discussion

111.	If a sample of germanium and a sample of silicon have the same impurity density and are kept at room temperature
Answer» Resistivity of silicon is more than that of germanium.

Discussion

112.	When an electric field E is applied to solid and liquid insulating materials, the internal field E acting at the location of atom is such that
Answer» The actual field seen by an atom is larger than applied field.

Discussion

113.	type semiconductors
Answer» n type semiconductors are produced by adding pentavalent material like phosphorus to silicon.

Discussion

114.	When two conductors carry currents in the same direction the force is repulsive.
Answer» The force is attractive.

Discussion

115.	The number of valence electrons in trivalent impurity is
Answer» Trivalent means 3 valence electrons.

Discussion

116.	Sulphur hexafluoride is used in
Answer» Sulphur hexafluoride is used in circuit breakers for arc quenching and insulation.

Discussion

117.	Material which lack permanent magnetic dipoles are known as
Answer» Diamagnetic materials have no permanent magnetic diploes.

Discussion

118.	A dielectric material must be
Answer» Any material other than insulator will short-circuit the plates.

Discussion

119.	In a metal, the valence electrons
Answer» In a metal the valence electrons belong to all atoms.

Discussion

120.	Which of these has lowest dielectric strength?
Answer» Cotton and paper have higher dielectric strength than air. Moisture decreases dielectric strength.

Discussion

121.	Two materials having temperature coefficients of 0.004 and 0.0004 respectively are joined in series. The overall temperature coefficient is likely to be
Answer» The overall temperature coefficient will be less than 0.004 and more than 0.0004.

Discussion

122.	Diamond is a paramagnetic material.
Answer» Diamond is diamagnetic.

Discussion

123.	Which capacitor-store higher amount of energy?
Answer» Energy stored is proportional to capacitance and capacitance is proportional to permittivity.

Discussion

124.	Above ferroelectric curie temperature, spontaneous polarization in ferroelectric materials becomes stronger.
Answer» Spontaneous polarization vanishes above ferro-electric Curie temperature.

Discussion

125.	In paramagnetic materials
Answer» In paramagnetic materials interaction between neighbouring dipoles is negligible.

Discussion

Explore topic-wise InterviewSolutions in .

The - relation for an arc is = 44 + . If = 50 V, =

The units for intrinsic strength of dielectric are

An atom of a rare gas is placed is an electric field E. Then

In van der walls crystals, there exists a high degree of stability of the outer electron shell.

In a coaxial cable, braided copper is used for

The hysteresis phenomenon in ferromagnetic materials exists at all temperatures.

If the radius of electron cloud around the nucleus of a rare gas atom is R, the electronic polarizability of the atom is porportional to

By inserting a plate of dielectric between the plates of a parallel plate capacitor, the energy stored in the capacitor is increased five times. The dielectric constant of material is

A parallel plate capacitor has its length, width and separation doubled. It fringing effects are neglected, to keep the capacitance same, the dielectric constant must be

In atomic physics, a state with = 0 is called state.

If a sample of germanium and a sample of silicon have the same impurity density and are kept at room temperature

When an electric field E is applied to solid and liquid insulating materials, the internal field E acting at the location of atom is such that

type semiconductors

When two conductors carry currents in the same direction the force is repulsive.

The number of valence electrons in trivalent impurity is

Sulphur hexafluoride is used in

Material which lack permanent magnetic dipoles are known as

A dielectric material must be

In a metal, the valence electrons

Which of these has lowest dielectric strength?

Two materials having temperature coefficients of 0.004 and 0.0004 respectively are joined in series. The overall temperature coefficient is likely to be

Diamond is a paramagnetic material.

Which capacitor-store higher amount of energy?

Above ferroelectric curie temperature, spontaneous polarization in ferroelectric materials becomes stronger.

In paramagnetic materials