9294 + Mcqs in Electronics and Communication Engineering Page 151 McqOptions

7501.	Hall effect is observed in a specimen (metal or semi- conductor) when it is carrying current and is placed in a magnetic field. The resultant electric field inside the specimen is
A.	normal to both current and magnetic field
B.	in the same direction as current
C.	in a direction anti parallel to magnetic field
D.	none of the above
Answer» B. in the same direction as current

Discussion

7502.	The capacitance of a capacitor is not affected by
A.	area of plates
B.	thickness of plates
C.
D.	<sub><i>r</i></sub>
E.	distance between plates
Answer» C.

Discussion

7503.	Assertion (A): In an intrinsic semiconductor J = ( n x p)eni.Reason (R): Intrinsic charge concentration ni at temperature T is given by ni2 = A0 T3 e-EG0/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» C. A is true but R is false

Discussion

7504.	Macroscopic quantities of a given material
A.	are absolutely constant
B.	are a function of temperature
C.	are a function of temperature, pressure field
D.	none of the above
Answer» E.

Discussion

7505.	For a superconductor, the relative permeability is
A.	zero
B.	high
C.	low
D.	either low or high
Answer» B. high

Discussion

7506.	The relative permeability of a ferromagnetic material is
A.	1
B.	less than 1
C.	about 10
D.	1000 or more
Answer» E.

Discussion

7507.	If v is velocity of electron, 0 is absolute permittivity, m is mass of electron, e is charge on electron and r is the radius of orbit of electron in hydrogen atom, the stability of orbit requires the following equation to be satisfied
A.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/28-1.png">
B.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/28-2.png">
C.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/28-3.png">
D.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/28-4.png">
Answer» C. <img src="/_files/images/electronics-and-communication-engineering/materials-and-components/28-3.png">

Discussion

7508.	Assertion (A): Ferrites are very useful at very high frequencies.Reason (R): Ferrites have high permeability and high resistivity.
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

7509.	In a conductor the current flow is due to
A.	holes
B.	electrons
C.	ions
D.	electrons and ions
Answer» C. ions

Discussion

7510.	Assertion (A): For a dielectric, P = 0( r - 1) E.Reason (R): Dipole moment per unit volume is called polarization of dielectric.
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

7511.	The current flow in a semiconductor is due to
A.	holes
B.	electrons
C.	holes and electrons
D.	holes, electrons and ions
Answer» D. holes, electrons and ions

Discussion

7512.	Some ceramic materials become superconducting
A.	below liquid helium temperature
B.	between liquid helium and liquid nitrogen temperature
C.	above liquid nitrogen but below room temperature
D.	at room temperature
Answer» B. between liquid helium and liquid nitrogen temperature

Discussion

7513.	Assertion (A): Doping level in extrinsic semiconductors is very small.Reason (R): Additional of impurity in the ratio of 1 part in 108 parts increases the number of charge carriers by about 20.
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

7514.	Assertion (A): Copper is a good conductor of electricity.Reason (R): Copper has a face centred cubic lattice.
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

7515.	When a dielectric is subjected to an electric field E, each volume element of dielectric can be considered to be carrying an electric dipole moment.
A.	True
B.	False
Answer» B. False

Discussion

7516.	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
Answer» B. False

Discussion

7517.	The core of an atom consists of
A.	nucleus
B.	nucleus and all orbits
C.	nucleus and inner orbits
D.	none of the above
Answer» D. none of the above

Discussion

7518.	Assertion (A): In ionic dielectrics, P = Pe + Pi.Reason (R): In ionic crystals, permanent electric dipole moment is 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

7519.	Assertion (A): Relative permittivity is determined by the atomic structure of the material.Reason (R): Absolute permittivity is determined by the atomic structure of the 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» D. A is false but R is true

Discussion

7520.	Consider the following statements An iron cored choke is non linear and passive device.A carbon resistor kept in sunlight is a time invariant and passive device.A dry cell is a time varying and active device.An air capacitor is time invariant and passive device. Of these statements
A.	1, 2, 3 and 4 are correct
B.	1, 2, 3 are correct
C.	1, 2, 4 are correct
D.	2 and 4 are correct
Answer» B. 1, 2, 3 are correct

Discussion

7521.	Which of these has the highest dielectric strength?
A.	Mica
B.	Air
C.	Cotton
D.	Rubber
Answer» B. Air

Discussion

7522.	For an insulating material, dielectric strength and dielectric losses should be
A.	high and high
B.	low and high
C.	high and low
D.	low and low
Answer» D. low and low

Discussion

7523.	A good dielectric should have
A.	low losses
B.	good heat conductivity
C.	high intrinsic strength
D.	all of the above
Answer» E.

Discussion

7524.	A single layer air cored coil has n turns and inductance L. If a new coil is formed by having 2n turns while keeping the coil length and diameter the same, the new inductance is
A.	0.5 L
B.	L
C.	2 L
D.	4 L
Answer» E.

Discussion

7525.	The colour code on a carbon resistor is yellow-violet-orange. The value of resistance is
A.	17000 &ohm;
B.	27000 &ohm;
C.	37000 &ohm;
D.	47000 &ohm;
Answer» E.

Discussion

7526.	Magnetic hysteresis phenomenon is explained by
A.	motion of domain walls
B.	motion of domain walls and domain rotation
C.	domain rotation
D.	none of the above
Answer» C. domain rotation

Discussion

7527.	The direction of force an a conductor carrying current and lying in a magnetic field can be found by using
A.	Fleming's left hand rule
B.	Fleming's right hand rule
C.	Cork screw rule
D.	Any of the above
Answer» B. Fleming's right hand rule

Discussion

7528.	Assertion (A): Rochelle salt and Barium titanate are both ferroelectric. Reason (R): Ferroelectric materials exhibit hysteresis effect.
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

7529.	If a metal specimen has n valence electrons per m3 each having charge e and mass m and t is the relaxations time, the conductivity is
A.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/100-1.png">
B.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/100-2.png">
C.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/100-3.png">
D.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/100-4.png">
Answer» C. <img src="/_files/images/electronics-and-communication-engineering/materials-and-components/100-3.png">

Discussion

7530.	M = ( r - 1)H.
A.	True
B.	False
Answer» B. False

Discussion

7531.	Silicon and germanium are elements in the
A.	second column of periodic table
B.	third column of periodic table
C.	fourth column of periodic table
D.	fifth column of periodic table
Answer» D. fifth column of periodic table

Discussion

7532.	Which of the following is used in temperature alarm circuits?
A.	Thermistor
B.	Photoconductor
C.	Transistor
D.	Varistor
Answer» B. Photoconductor

Discussion

7533.	A metal has a large number of free electrons. If e is electronic charge and m is mass of electron and an electric field E is applied along (say) x direction, the electrons acquire a velocity having a component vx is x direction. Then
A.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/97-1.png">
B.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/97-2.png">
C.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/97-3.png">
D.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/97-4.png">
Answer» D. <img src="/_files/images/electronics-and-communication-engineering/materials-and-components/97-4.png">

Discussion

7534.	When temperature is above ferromagnetic Curie temperature, a ferromagnetic material
A.	becomes a paramagnetic material
B.	becomes a very strong ferromagnetic material
C.	becomes diamagnetic material
D.	none of the above
Answer» B. becomes a very strong ferromagnetic material

Discussion

7535.	A magnet does not attract
A.	nickel
B.	iron
C.	copper
D.	iron and copper
Answer» D. iron and copper

Discussion

7536.	Bitter powder patterns prove the existence of domains.
A.	True
B.	False
Answer» B. False

Discussion

7537.	Assertion (A): An amorphous material is obtained when mobility of atoms is inhibited during solidification. Reason (R): Crystalline state is a natural state for most solids.
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

7538.	Soft iron is suitable for making temporary magnets.
A.	True
B.	False
Answer» B. False

Discussion

7539.	Antiferromagnetic materials do not have permanent dipoles.
A.	True
B.	False
Answer» C.

Discussion

7540.	The measurement of Hall coefficient of a semiconductor with one type of charge carriers gives the information about
A.	sign of charge carrier
B.	density of charge carrier
C.	both sign and density of charge carrier
D.	none of the above
Answer» D. none of the above

Discussion

7541.	0 has no other physical meaning than that of a fundamental conversion factor.
A.	True
B.	False
Answer» B. False

Discussion

7542.	The number of turns in a coil is doubled. If initial time constant is T, the new time constant is
A.	T
B.	2T
C.	4T
D.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/229-1.png">
Answer» C. 4T

Discussion

7543.	When a potential is applied across an intrinsic semiconductor, holes flow
A.	towards positive terminal
B.	away from positive terminal
C.	in the external circuit only
D.	none of the above
Answer» C. in the external circuit only

Discussion

7544.	Iron has a body centred cubic structure.
A.	True
B.	False
Answer» B. False

Discussion

7545.	The units of polarization of dielectric are
A.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/47-1.png">
B.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/47-2.png">
C.	C
D.	<i>m</i>
E.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/47-3.png">
Answer» B. <img src="/_files/images/electronics-and-communication-engineering/materials-and-components/47-2.png">

Discussion

7546.	Assertion (A): In a conductor, current density remains constant in time as long as E is constant.Reason (R): In a conductor, J = 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» B. Both A and R are true but R is not correct explanation of A

Discussion

7547.	n type semiconductors
A.	are negatively charged
B.	are produced when indium as impurity is added to germanium
C.	are produced phosphorus as impurity is added to silicon
D.	none of the above
Answer» D. none of the above

Discussion

7548.	The most important primary force of attraction in the formation of solids is
A.	electromagnetic
B.	electrostatic
C.	quantum-electrostatic
D.	quantum electromagnetic
Answer» C. quantum-electrostatic

Discussion

7549.	When two conductors carry currents in the same direction the force is repulsive.
A.	True
B.	False
Answer» C.

Discussion

7550.	Which of the following is used in automatic control of street lights?
A.	Thermistor
B.	Photoconductor
C.	Transistor
D.	Varistor
Answer» C. Transistor

Discussion

Explore topic-wise MCQs in Engineering.

Hall effect is observed in a specimen (metal or semi- conductor) when it is carrying current and is placed in a magnetic field. The resultant electric field inside the specimen is

The capacitance of a capacitor is not affected by

Assertion (A): In an intrinsic semiconductor J = ( n x p)eni.Reason (R): Intrinsic charge concentration ni at temperature T is given by ni2 = A0 T3 e-EG0/kT.

Macroscopic quantities of a given material

For a superconductor, the relative permeability is

The relative permeability of a ferromagnetic material is

If v is velocity of electron, 0 is absolute permittivity, m is mass of electron, e is charge on electron and r is the radius of orbit of electron in hydrogen atom, the stability of orbit requires the following equation to be satisfied

Assertion (A): Ferrites are very useful at very high frequencies.Reason (R): Ferrites have high permeability and high resistivity.

In a conductor the current flow is due to

Assertion (A): For a dielectric, P = 0( r - 1) E.Reason (R): Dipole moment per unit volume is called polarization of dielectric.

The current flow in a semiconductor is due to

Some ceramic materials become superconducting

Assertion (A): Doping level in extrinsic semiconductors is very small.Reason (R): Additional of impurity in the ratio of 1 part in 108 parts increases the number of charge carriers by about 20.

Assertion (A): Copper is a good conductor of electricity.Reason (R): Copper has a face centred cubic lattice.

When a dielectric is subjected to an electric field E, each volume element of dielectric can be considered to be carrying an electric dipole moment.

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".

The core of an atom consists of

Assertion (A): In ionic dielectrics, P = Pe + Pi.Reason (R): In ionic crystals, permanent electric dipole moment is zero.

Assertion (A): Relative permittivity is determined by the atomic structure of the material.Reason (R): Absolute permittivity is determined by the atomic structure of the material.

Consider the following statements An iron cored choke is non linear and passive device.A carbon resistor kept in sunlight is a time invariant and passive device.A dry cell is a time varying and active device.An air capacitor is time invariant and passive device. Of these statements

Which of these has the highest dielectric strength?

For an insulating material, dielectric strength and dielectric losses should be

A good dielectric should have

A single layer air cored coil has n turns and inductance L. If a new coil is formed by having 2n turns while keeping the coil length and diameter the same, the new inductance is

The colour code on a carbon resistor is yellow-violet-orange. The value of resistance is

Magnetic hysteresis phenomenon is explained by

The direction of force an a conductor carrying current and lying in a magnetic field can be found by using

Assertion (A): Rochelle salt and Barium titanate are both ferroelectric. Reason (R): Ferroelectric materials exhibit hysteresis effect.

If a metal specimen has n valence electrons per m3 each having charge e and mass m and t is the relaxations time, the conductivity is

M = ( r - 1)H.

Silicon and germanium are elements in the

Which of the following is used in temperature alarm circuits?

A metal has a large number of free electrons. If e is electronic charge and m is mass of electron and an electric field E is applied along (say) x direction, the electrons acquire a velocity having a component vx is x direction. Then

When temperature is above ferromagnetic Curie temperature, a ferromagnetic material

A magnet does not attract

Bitter powder patterns prove the existence of domains.

Assertion (A): An amorphous material is obtained when mobility of atoms is inhibited during solidification. Reason (R): Crystalline state is a natural state for most solids.

Soft iron is suitable for making temporary magnets.

Antiferromagnetic materials do not have permanent dipoles.

The measurement of Hall coefficient of a semiconductor with one type of charge carriers gives the information about

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

The number of turns in a coil is doubled. If initial time constant is T, the new time constant is

When a potential is applied across an intrinsic semiconductor, holes flow

Iron has a body centred cubic structure.

The units of polarization of dielectric are

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

n type semiconductors

The most important primary force of attraction in the formation of solids is

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

Which of the following is used in automatic control of street lights?