595 + Mcqs in Materials And Components Page 3 McqOptions

101.	Assertion (A): Electronic polarizability increases as atoms becomes larger.Reason (R): For rare gas, ∈₀(∈ᵣ - 1) E = Nαe, where N is number of atoms/m³ and αe is electronic polarizability of material.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» C. A is true but R is false

Discussion

102.	Silicon and germanium have diamond structure. The number of atoms in a volume equal to a³ where a is the edge of elementary cube are
A.	32
B.	16
C.	8
D.	4
Answer» D. 4

Discussion

103.	Assertion (A): In a conductor, current density remains constant in time as long as E is constant.Reason (R): In a conductor, J = σE.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

104.	A rare gas has N atoms per m³. If electronic polarizability of single atom of this gas is αe, then
A.	∈ᵣ = Nαe
B.	∈₀∈ᵣ = Nαe
C.	∈₀(∈ᵣ - 1) = Nαe
D.	∈₀(∈ᵣ - 2) = Nαe
Answer» D. ∈₀(∈ᵣ - 2) = Nαe

Discussion

105.	Lines of magnetic field attract each other.
A.	True
B.	False
C.	May be True or False
D.	Can't say
Answer» C. May be True or False

Discussion

106.	The number of valence electrons in pentavalent impurity is
A.	5
B.	4
C.	3
D.	1
Answer» B. 4

Discussion

107.	Assertion (A): CO₂ has no resultant dipole moment but CO has a dipole moment.Reason (R): The structure of CO₂ is O = C = O.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

108.	Assertion (A): Orbital magnetic moment of an electron in an atom is of the order of 1 Bohr magneton.Reason (R): 1 Bohr magneton = 9.27 x 10^-24 A/m².
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» C. A is true but R is false

Discussion

109.	When subjected to alternating stresses, an insulating material is characterised by complex dielectric constant ∈'r - j∈"r . In such materials, the dielectric losses under alternating stress is proportional
A.	∈"r
B.	both ∈'r and ∈"r
C.	∈'r
D.	(∈"r)2
Answer» B. both ∈'r and ∈"r

Discussion

110.	An iron specimen has µᵣ = 1000 when B = 0.3 T. If B = 0.35 T, µᵣ
A.	will be 1000
B.	will be less than 1000
C.	will be more than 1000
D.	may be more or less than 1000
Answer» E.

Discussion

111.	A sample of N type semiconductor has an electron density of 6.25 x 10¹⁸/cm³ at 300 K. If intrinsic concentration of carriers in this sample is 2.5 x 10¹³/cm³ at this temperature, the hole density is
A.	10⁶ / cm³
B.	10⁸ / cm³
C.	10¹ᴼ / cm³
D.	10¹² / cm³
Answer» C. 10¹ᴼ / cm³

Discussion

112.	Assertion (A): The equation D = ∈₀∈ᵣE is applicable only to isotropic materials.Reason (R): In polycrystalline materials, the directional effects are absent.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» C. A is true but R is false

Discussion

113.	∈₀ has no other physical meaning than that of a fundamental conversion factor.
A.	True
B.	False
C.	May be True or False
D.	Can't say
Answer» B. False

Discussion

114.	In a specimen of ferromagnetic material, as the flux density is increased from zero to 2.5 T, µᵣ will
A.	increase
B.	decrease
C.	first decrease then increase
D.	first increase then decrease
Answer» E.

Discussion

115.	Yettrium-iron garnet (Y₂Fe₅O₁₂) is a soft magnetic material suitable for applications involving
A.	dc
B.	50 Hz ac
C.	ac of a few K Hz
D.	ac of a few hundred MHz
Answer» B. 50 Hz ac

Discussion

116.	The law that K/σT (where K is thermal conductivity, σ is electrical conductivity and T is absolute temperature) for all metals is equal to a universal constant is known as
A.	Lorentz law
B.	Wiedemann Franz law
C.	Curie Weiss law
D.	Kittel law
Answer» B. Wiedemann Franz law

Discussion

117.	Diamond is a paramagnetic material.
A.	True
B.	False
C.	May be True or False
D.	Can't say
Answer» C. May be True or False

Discussion

118.	Two materials having temperature coefficients of 0.004 and 0.0004 respectively are joined in series. The overall temperature coefficient is likely to be
A.	0.08
B.	0.04
C.	0.001
D.	0.0001
Answer» D. 0.0001

Discussion

119.	The minority carrier life time and diffusion constant in a semiconducting material are 100 μs and 100 cm²/s respectively. The diffusion length of carriers is
A.	0.1 cm
B.	0.01 cm
C.	0.0141 cm
D.	1 cm
Answer» B. 0.01 cm

Discussion

120.	The core of a solenoid is made of material of relative permeability μᵣ. A small cavity area dA and length dl is cut in the core. If it is desired that flux density in the cavity should be equal to B0
A.	the fields inside and outside the cavity must be equal
B.	the field inside the cavity must be made stronger than field outside the cavity
C.	the field inside the cavity must be made weaker than the field outside the cavity
D.	none of the above
Answer» C. the field inside the cavity must be made weaker than the field outside the cavity

Discussion

121.	The equation D = ∈₀∈ᵣ E refers only to isotropic materials.
A.	True
B.	False
C.	May be True or False
D.	Can't say
Answer» B. False

Discussion

122.	A piece of copper and another piece of Germanium are cooled from 30°C to 80 K. The resistance of
A.	copper decreases and germanium increases
B.	both decreases
C.	both increases
D.	copper increases and germanium decreases
Answer» B. both decreases

Discussion

123.	Curie Weiss law is Ɛ = C/(T-ϴ) .
A.	True
B.	False
C.	May be True or False
D.	Can't say
Answer» B. False

Discussion

124.	Electrical conductivity of metals expressed in ohm¯¹ m¯¹ is of the order of
A.	10¹ᴼ
B.	10⁵
C.	10¯⁴
D.	10¯⁶
Answer» C. 10¯⁴

Discussion

125.	Assertion (A): For elemental dielectrics, P = NaeEi where N is number of atoms/m³, P is polarization, ae is electronic polarization and Ei is internal electric field.Reason (R): In elemental dielectrics there are no permanent dipoles or ions.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

126.	Assertion (A): ∈₀ has the dimensions of farad per meter.Reason (R): D = ∈₀∈ᵣ E.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» C. A is true but R is false

Discussion

127.	As per Bohr's postulate, only those circular orbits are stable for which the angular momentum is equal to an integer times h/2π .
A.	True
B.	False
C.	May be True or False
D.	Can't say
Answer» B. False

Discussion

128.	Assertion (A): In imperfect capacitors, the current does not lead the applied ac voltage by 90°.Reason (R): When subjected to ac fields, the dielectric constant can be expressed as ∈'r - j∈"r.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

129.	Assertion (A): Magnetic susceptibility of diamagnetic materials is much less than that of paramagnetic materials.Reason (R): For diamagnetic as well as paramagnetic materials, μᵣ is nearly equal to 1.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

130.	Assertion (A): If WF is Fermi energy, v is velocity of electron and m is mass of electron, then 1/2mv² = WF .Reason (R): Conductivity of a metal depends on temperature and impurity concentration.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» C. A is true but R is false

Discussion

131.	The law J = σE, where J is current density, σ is electrical conductivity and E is field strength is
A.	Ohm's law
B.	Gauss law
C.	Ampere's law
D.	Biot-Savart law
Answer» B. Gauss law

Discussion

132.	Assertion (A): In some materials, Ɛᵣ is independent of temperature while in others, Ɛᵣ depends on temperature.Reason (R): If permanent dipoles are absent, Ɛᵣ varies with temperature.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» D. A is false but R is true

Discussion

133.	If ∈ᵣ = ∈ᵣ' - j∈ᵣ" tan δ = ∈ᵣ'/∈ᵣ".
A.	True
B.	False
C.	May be True or False
D.	Can't say
Answer» B. False

Discussion

134.	Assertion (A): When cathode temperature is increased from 2500 K to 2550 K, thermionic emission current may increase by about 50%.Reason (R): Thermionic emission current ∝ T² e^(-Ew/kT).
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

135.	Consider the following statement:If an electric field is applied to an n type semiconductor bar, the electrons and holes move in opposite directions due to their opposite charges. The net currents is 1. both due to electrons and holes with electrons as majority carriers2. sum of hole and electron currents3. difference between electron and hole currents. Which of above statements are correct?
A.	1 only
B.	1 and 2
C.	2 only
D.	3 only
Answer» C. 2 only

Discussion

136.	If q is charge on an electron, R is radius of electron orbit and ω is angular velocity of electron rotation, the magnetic dipole moment of electron in orbit is
A.	0.5 qωR
B.	0.5 q²ω²R²
C.	0.5 qωR²
D.	0.5 qω²R
Answer» D. 0.5 qω²R

Discussion

137.	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.	1/25
B.	1/5
C.	5
D.	25
Answer» D. 25

Discussion

138.	Assertion (A): The resistance of a copper specimen changes by about 22% when temperature is increased from room temperature to 700°C.Reason (R): The physical properties of a material are determined mostly by the extent of impurities.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» C. A is true but R is false

Discussion

139.	Eddy current loss is
A.	proportional to frequency
B.	independent of frequency
C.	proportional to (frequency)²
D.	proportional to (frequency)³
Answer» D. proportional to (frequency)³

Discussion

140.	Assertion (A): The optical dielectric constant (i.e., εr at optical frequencies)of ionic dielectrics is less than static dielectric constant. Reason (R): At optical frequencies, Pi = 0.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

141.	Assertion (A): An electron having charge - e and mass m and lying in an electric field E is subjected to an acceleration - (e/m) E.Reason (R): If there are n electrons/m³ moving with velocity vᵪ and each electron has a charge - e, the current density J = - n evᵪ.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» C. A is true but R is false

Discussion

142.	Assertion (A): For Diamond, μᵣ = 1Reason (R): Diamond is a diamagnetic material.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

143.	In which of the following semiconductor are holes majority carriers
A.	intrinsic
B.	extrinsic
C.	p type
D.	n type
Answer» D. n type

Discussion

144.	A leaky dielectric has ∈ᵣ = ∈ᵣ' - j∈ᵣ". If a field E is applied, the current component in phase with E is proportional to ∈ᵣ".
A.	True
B.	False
C.	May be True or False
D.	Can't say
Answer» B. False

Discussion

145.	Assertion (A): Ferroelectric materials have spontaneous polarization.Reason (R): Above curie temperature, ∈ = C/(T-ϴ) for ferro-electric materials.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» C. A is true but R is false

Discussion

146.	Assertion (A): Power loss in a conductor of resistance P = I²R.Reason (R): When a conductor is carrying current with current density J as a result of applied field E, then heat developed/m³/ second = JE.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

147.	In an homogeneous dielectric subjected to an electric field E, the dipole moment per unit volume is ∈₀(∈ᵣ - 1) E.
A.	True
B.	False
C.	May be True or False
D.	Can't say
Answer» B. False

Discussion

148.	If ω₀ is the angular frequency of rotation of electron in the absence of magnetic field, the angular frequency ω, when a magnetic field B is acting is ω ≅ ω₀ + (e/2m)B.
A.	True
B.	False
C.	May be True or False
D.	Can't say
Answer» B. False

Discussion

149.	Assertion (A): In a perfect capacitor, the current density is given by ω ∈₀E0∈'rcos(ωt + 90°), where ∈ᵣ' is real part of dielectric constant.Reason (R): In a perfect capacitor, dielectric losses are zero.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true but R is not correct explanation of A

Discussion

150.	Assertion (A): For a solenoid having N turns, B = µ₀µᵣNI/L .Reason (R): For all magnetic materials, B increases linearly with I.
A.	Both A and R are true and R is correct explanation of A
B.	Both A and R are true but R is not correct explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» D. A is false but R is true

Discussion

Explore topic-wise MCQs in Electronics & Communication Engineering.

Assertion (A): Electronic polarizability increases as atoms becomes larger.Reason (R): For rare gas, ∈₀(∈ᵣ - 1) E = Nαe, where N is number of atoms/m³ and αe is electronic polarizability of material.

Silicon and germanium have diamond structure. The number of atoms in a volume equal to a³ where a is the edge of elementary cube are

Assertion (A): In a conductor, current density remains constant in time as long as E is constant.Reason (R): In a conductor, J = σE.

A rare gas has N atoms per m³. If electronic polarizability of single atom of this gas is αe, then

Lines of magnetic field attract each other.

The number of valence electrons in pentavalent impurity is

Assertion (A): CO₂ has no resultant dipole moment but CO has a dipole moment.Reason (R): The structure of CO₂ is O = C = O.

Assertion (A): Orbital magnetic moment of an electron in an atom is of the order of 1 Bohr magneton.Reason (R): 1 Bohr magneton = 9.27 x 10^-24 A/m².

When subjected to alternating stresses, an insulating material is characterised by complex dielectric constant ∈'r - j∈"r . In such materials, the dielectric losses under alternating stress is proportional

An iron specimen has µᵣ = 1000 when B = 0.3 T. If B = 0.35 T, µᵣ

A sample of N type semiconductor has an electron density of 6.25 x 10¹⁸/cm³ at 300 K. If intrinsic concentration of carriers in this sample is 2.5 x 10¹³/cm³ at this temperature, the hole density is

Assertion (A): The equation D = ∈₀∈ᵣE is applicable only to isotropic materials.Reason (R): In polycrystalline materials, the directional effects are absent.

∈₀ has no other physical meaning than that of a fundamental conversion factor.

In a specimen of ferromagnetic material, as the flux density is increased from zero to 2.5 T, µᵣ will

Yettrium-iron garnet (Y₂Fe₅O₁₂) is a soft magnetic material suitable for applications involving

The law that K/σT (where K is thermal conductivity, σ is electrical conductivity and T is absolute temperature) for all metals is equal to a universal constant is known as

Diamond is a paramagnetic material.

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

The minority carrier life time and diffusion constant in a semiconducting material are 100 μs and 100 cm²/s respectively. The diffusion length of carriers is

The core of a solenoid is made of material of relative permeability μᵣ. A small cavity area dA and length dl is cut in the core. If it is desired that flux density in the cavity should be equal to B0

The equation D = ∈₀∈ᵣ E refers only to isotropic materials.

A piece of copper and another piece of Germanium are cooled from 30°C to 80 K. The resistance of

Curie Weiss law is Ɛ = C/(T-ϴ) .

Electrical conductivity of metals expressed in ohm¯¹ m¯¹ is of the order of

Assertion (A): For elemental dielectrics, P = NaeEi where N is number of atoms/m³, P is polarization, ae is electronic polarization and Ei is internal electric field.Reason (R): In elemental dielectrics there are no permanent dipoles or ions.

Assertion (A): ∈₀ has the dimensions of farad per meter.Reason (R): D = ∈₀∈ᵣ E.

As per Bohr's postulate, only those circular orbits are stable for which the angular momentum is equal to an integer times h/2π .

Assertion (A): In imperfect capacitors, the current does not lead the applied ac voltage by 90°.Reason (R): When subjected to ac fields, the dielectric constant can be expressed as ∈'r - j∈"r.

Assertion (A): Magnetic susceptibility of diamagnetic materials is much less than that of paramagnetic materials.Reason (R): For diamagnetic as well as paramagnetic materials, μᵣ is nearly equal to 1.

Assertion (A): If WF is Fermi energy, v is velocity of electron and m is mass of electron, then 1/2mv² = WF .Reason (R): Conductivity of a metal depends on temperature and impurity concentration.

The law J = σE, where J is current density, σ is electrical conductivity and E is field strength is

Assertion (A): In some materials, Ɛᵣ is independent of temperature while in others, Ɛᵣ depends on temperature.Reason (R): If permanent dipoles are absent, Ɛᵣ varies with temperature.

If ∈ᵣ = ∈ᵣ' - j∈ᵣ" tan δ = ∈ᵣ'/∈ᵣ".

Assertion (A): When cathode temperature is increased from 2500 K to 2550 K, thermionic emission current may increase by about 50%.Reason (R): Thermionic emission current ∝ T² e^(-Ew/kT).

If q is charge on an electron, R is radius of electron orbit and ω is angular velocity of electron rotation, the magnetic dipole moment of electron in orbit is

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

Assertion (A): The resistance of a copper specimen changes by about 22% when temperature is increased from room temperature to 700°C.Reason (R): The physical properties of a material are determined mostly by the extent of impurities.

Eddy current loss is

Assertion (A): The optical dielectric constant (i.e., εr at optical frequencies)of ionic dielectrics is less than static dielectric constant. Reason (R): At optical frequencies, Pi = 0.

Assertion (A): An electron having charge - e and mass m and lying in an electric field E is subjected to an acceleration - (e/m) E.Reason (R): If there are n electrons/m³ moving with velocity vᵪ and each electron has a charge - e, the current density J = - n evᵪ.

Assertion (A): For Diamond, μᵣ = 1Reason (R): Diamond is a diamagnetic material.

In which of the following semiconductor are holes majority carriers

A leaky dielectric has ∈ᵣ = ∈ᵣ' - j∈ᵣ". If a field E is applied, the current component in phase with E is proportional to ∈ᵣ".

Assertion (A): Ferroelectric materials have spontaneous polarization.Reason (R): Above curie temperature, ∈ = C/(T-ϴ) for ferro-electric materials.

Assertion (A): Power loss in a conductor of resistance P = I²R.Reason (R): When a conductor is carrying current with current density J as a result of applied field E, then heat developed/m³/ second = JE.

In an homogeneous dielectric subjected to an electric field E, the dipole moment per unit volume is ∈₀(∈ᵣ - 1) E.

If ω₀ is the angular frequency of rotation of electron in the absence of magnetic field, the angular frequency ω, when a magnetic field B is acting is ω ≅ ω₀ + (e/2m)B.

Assertion (A): In a perfect capacitor, the current density is given by ω ∈₀E0∈'rcos(ωt + 90°), where ∈ᵣ' is real part of dielectric constant.Reason (R): In a perfect capacitor, dielectric losses are zero.

Assertion (A): For a solenoid having N turns, B = µ₀µᵣNI/L .Reason (R): For all magnetic materials, B increases linearly with I.