9294 + Mcqs in Electronics and Communication Engineering Page 154 McqOptions

7651.	Assertion (A): For most metals, Fermi energy EF is less than 10 eV.Reason (R): Fermi level of a metal is given by EF = 3.64 x 10-19 (n)2/3 where n is number of free electrons/m3 of metal.
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

7652.	The orientation polarization is directly proportional to temperatureinversely proportional to temperatureinversely proportional to square of permanent dipole momentdirectly proportional to square of permanent dipole moment. Which of the above are correct?
A.	1 and 3 only
B.	2 and 3 only
C.	1 and 4 only
D.	2 and 4 only
Answer» E.

Discussion

7653.	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 vx and each electron has a charge - e, the current density J = - n evx.
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

7654.	The law that (where K is thermal conductivity, 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

7655.	In elemental dielectrics, the orientation and ionic polarization are absent.
A.	True
B.	False
Answer» B. False

Discussion

7656.	An electrolytic capacitor can be used for
A.	ac only
B.	dc only
C.	both ac and dc
D.	high frequency ac
Answer» C. both ac and dc

Discussion

7657.	The dielectrics having only one kind of atoms are known as elemental dielectrics.
A.	True
B.	False
Answer» B. False

Discussion

7658.	At a very low temperature, a semiconductor
A.	becomes a conductor
B.	becomes an insulator
C.	may become a conductor or an insulator
D.	will remain a semiconductor becomes a conductor or an insulator
Answer» C. may become a conductor or an insulator

Discussion

7659.	In crystalline solids, atoms are stacked in a regular manner.
A.	True
B.	False
Answer» B. False

Discussion

7660.	The temperature below which certain materials are antiferromagnetic and above which they are paramagnetic is called
A.	Weiss temperature
B.	Curie temperature
C.	Neel temperature
D.	None of the above
Answer» D. None of the above

Discussion

7661.	In metals, the average drift velocity of electron per unit field is called mobility.
A.	True
B.	False
Answer» B. False

Discussion

7662.	Some typical examples of macroscopic quantities are
A.	conductivity
B.
C.	<sub><i>r</i></sub>
D.	dielectric constant
E.	all of the above
Answer» E. all of the above

Discussion

7663.	The temperature coefficient of a thermistor
A.	is positive
B.	is negative
C.	zero
D.	may be positive or negative depending on its composition
Answer» C. zero

Discussion

7664.	Assertion (A): Helium, Argon and Neon are gaseous at room temperature.Reason (R): The atoms in Helium, Argon and Neon are chemically extremely inactive.
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

7665.	The colour code on a carbon resistor is red-red-black-silver. The value of resistor is
A.	22000 &ohm;
B.	2200 &ohm;
C.	22 5% &ohm;
D.	22 10% &ohm;
Answer» E.

Discussion

7666.	In intrinsic semiconductors, the number of free electrons is equal to the number of mobile holes.
A.	True
B.	False
Answer» B. False

Discussion

7667.	If the valence electron is separated from a copper atom, the remaining part of atom has a net charge of
A.	1
B.	- 1
C.	0
D.	+ 3
Answer» B. - 1

Discussion

7668.	If eddy current damping is to be used, the disc of instrument should be
A.	non-conducting and non-magnetic
B.	conducting and magnetic
C.	conducting and non-magnetic
D.	non-conducting and magnetic
Answer» D. non-conducting and magnetic

Discussion

7669.	The scale of moving iron instrument is linear.
A.	True
B.	False
Answer» C.

Discussion

7670.	With a variable reluctance tachometer having 60 rotor teeth the count reads 3600 counts per minute. The speed in RPM is
A.	36
B.	60
C.	360
D.	3600
Answer» C. 360

Discussion

7671.	Consider the following operation in respect of Wheatstone bridge (Kb, denotes battery key, Kg denotes galvanometer key) open Kbclose Kgclose Kbopen Kg The correct sequence of operations is
A.	1, 2, 3, 4
B.	3, 1, 2, 4
C.	4, 3, 2, 1
D.	3, 2, 4, 1
Answer» E.

Discussion

7672.	A meter having 0-1000 A range and 1000 &ohm; resistance is required to be changed to 0-100 mA meter. The value of shunt resistance is about
A.	1 &ohm;
B.	10 &ohm;
C.	99 &ohm;
D.	100 &ohm;
Answer» C. 99 &ohm;

Discussion

7673.	When measuring phase angle between two waves using a CRO, the time base generator is connected to
A.	X plate
B.	Y plate
C.	both X and Y plate
D.	neither X nor Y plates
Answer» E.

Discussion

7674.	Two voltmeters 0-250 V each having resistances of 5 k&ohm; and 10 k&ohm; respectively and are connected in series. To ensure that neither of them goes beyond scale the total voltage which can be applied should be less than
A.	500 V
B.	400 V
C.	375 V
D.	250 V
Answer» D. 250 V

Discussion

7675.	A 24 mm long conductor has a resistance of 128 &ohm;. The change in resistance is 13.3 &ohm; and change in length is 1.6 mm under tension. The gauge factor is
A.	1.2
B.	1.6
C.	2.1
D.	2.6
Answer» C. 2.1

Discussion

7676.	A meter has a square law scale. For 2 A current the deflection in 90 . For a deflection of 45 , the current is
A.	1 A
B.	1.5 A
C.	1.414 A
D.	1.61 A
Answer» D. 1.61 A

Discussion

7677.	Measuring of unknown voltage with a dc potentiometer loses its advantage of open circuit measurement when
A.	primary circuit battery is changed
B.	standardisation is done to compensate for drift
C.	voltage is larger than range of potentiometer
D.	range reduction by factor of 10 is employed
Answer» E.

Discussion

7678.	It is required that a strain gauge has gauge factor of 100. The proper strain gauge is
A.	constantan strain gauge
B.	nichrome strain gauge
C.	semiconductor strain gauge
D.	alloy strain gauge
Answer» D. alloy strain gauge

Discussion

7679.	Assertion (A): Metals are better heat conductors than insulators.Reason (R): If is temperature gradient, Q is heat flow density and K is thermal conductivity, then Q = - K (dT/dx).
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

7680.	In a polyatomic gas, the types of polarization which exist together are
A.	electronic and orientational
B.	electronic and ionic
C.	ionic and orientational
D.	electronic, orientational and ionic
Answer» E.

Discussion

7681.	At T = 0, the resistivity of a perfect single crystal of a metal is
A.	0
B.	low
C.	high
D.	finite
Answer» B. low

Discussion

7682.	In figure, the position of voltmeter and ammeter are exchanged. It may result in damage to
A.	both the instruments
B.	ammeter
C.	voltmeter
D.	neither of two
Answer» C. voltmeter

Discussion

7683.	Lines of magnetic field cannot intersect.
A.	True
B.	False
Answer» B. False

Discussion

7684.	The volt ratio box is basically a
A.	potential divider
B.	current transformer
C.	a high resistance voltmeter
D.	either (a) or (c)
Answer» B. current transformer

Discussion

7685.	A sinusoidal ac voltage of amplitude 100 V is applied to a rectifying device which offers 10 &ohm; resistance in forward direction and infinite resistance in backward direction. A moving coil ammeter is also connected in the circuit. The reading of ammeter will be
A.	10 A
B.	5 A
C.	3.185 A
D.	14.14 A
Answer» D. 14.14 A

Discussion

7686.	A variable reluctance tachometer has 180 teeth on rotor. The speed of shaft on which it is mounted in 1200 rpm. The frequency of output pulses is
A.	1800 per second
B.	3600 per second
C.	4800 per second
D.	5600 per second
Answer» C. 4800 per second

Discussion

7687.	The number of tightly bound electrons in silicon atom are
A.	14
B.	10
C.	6
D.	4
Answer» C. 6

Discussion

7688.	The iron core of a coil is removed so that it becomes an air cored coil. Its inductance will
A.	increase
B.	decrease
C.	remain the same
D.	may increase or decrease
Answer» C. remain the same

Discussion

7689.	A circular sphere mile is the area of cross-section of a wire
A.	having a diameter equal to 1 miles
B.	having a radius equal to 1 miles
C.	having a circumference equal to 1 miles
D.	none of the above
Answer» B. having a radius equal to 1 miles

Discussion

7690.	In an hydrogen atom, an electron moves in the field of a proton. The stability of orbit requires equilibrium between coulomb's force and centrifugal force.
A.	True
B.	False
Answer» B. False

Discussion

7691.	A particle of charge Q coulombs is bound elastically to an equilibrium position with a force constant of f newton per metre. The polarizability of the system is
A.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/60-1.png">
B.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/60-2.png">
C.	<img src="/_files/images/electronics-and-communication-engineering/materials-and-components/60-3.png">
D.	Q
E.	<i>f</i>
Answer» C. <img src="/_files/images/electronics-and-communication-engineering/materials-and-components/60-3.png">

Discussion

7692.	1 Bohr magneton = .
A.	True
B.	False
Answer» B. False

Discussion

7693.	The orientation polarization of a polyatomic gas is inversely proportional to absolute temperature.
A.	True
B.	False
Answer» B. False

Discussion

7694.	For small size high frequency coils, the most common core material is
A.	air
B.	ferrite
C.	powdered iron
D.	steel
Answer» B. ferrite

Discussion

7695.	In a virgin specimen of iron, the direction of spontaneous magnetisation varies from domain to domain.
A.	True
B.	False
Answer» B. False

Discussion

7696.	Which of the following is used in lightning arresters?
A.	Thermistor
B.	Photoconductor
C.	Transistor
D.	Varistor
Answer» E.

Discussion

7697.	High frequency inductors and capacitors are commonly plated with silver. The main purpose of this is to
A.	reduce dc resistance
B.	reduce ac resistance
C.	increase dc resistance
D.	increase ac resistance
Answer» C. increase dc resistance

Discussion

7698.	In its lowest state, the electron is bound to the field of proton by an energy equal to
A.	100.5 eV
B.	51.2 eV
C.	13.6 eV
D.	0.2 eV
Answer» D. 0.2 eV

Discussion

7699.	In a ferromagnetic material, the internal field seen by a dipole is
A.	equal to applied field
B.	equal to applied field minus a contribution from neighbouring dipoles
C.	equal to applied field plus a contribution from neighbouring dipoles
D.	equal to or less than applied field
Answer» D. equal to or less than applied field

Discussion

7700.	An induction wattmeter can be used for
A.	dc only
B.	50 Hz ac only
C.	both ac and dc
D.	high frequency ac only
Answer» C. both ac and dc

Discussion

Explore topic-wise MCQs in Engineering.

Assertion (A): For most metals, Fermi energy EF is less than 10 eV.Reason (R): Fermi level of a metal is given by EF = 3.64 x 10-19 (n)2/3 where n is number of free electrons/m3 of metal.

The orientation polarization is directly proportional to temperatureinversely proportional to temperatureinversely proportional to square of permanent dipole momentdirectly proportional to square of permanent dipole moment. Which of the above are correct?

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 vx and each electron has a charge - e, the current density J = - n evx.

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

In elemental dielectrics, the orientation and ionic polarization are absent.

An electrolytic capacitor can be used for

The dielectrics having only one kind of atoms are known as elemental dielectrics.

At a very low temperature, a semiconductor

In crystalline solids, atoms are stacked in a regular manner.

The temperature below which certain materials are antiferromagnetic and above which they are paramagnetic is called

In metals, the average drift velocity of electron per unit field is called mobility.

Some typical examples of macroscopic quantities are

The temperature coefficient of a thermistor

Assertion (A): Helium, Argon and Neon are gaseous at room temperature.Reason (R): The atoms in Helium, Argon and Neon are chemically extremely inactive.

The colour code on a carbon resistor is red-red-black-silver. The value of resistor is

In intrinsic semiconductors, the number of free electrons is equal to the number of mobile holes.

If the valence electron is separated from a copper atom, the remaining part of atom has a net charge of

If eddy current damping is to be used, the disc of instrument should be

The scale of moving iron instrument is linear.

With a variable reluctance tachometer having 60 rotor teeth the count reads 3600 counts per minute. The speed in RPM is

Consider the following operation in respect of Wheatstone bridge (Kb, denotes battery key, Kg denotes galvanometer key) open Kbclose Kgclose Kbopen Kg The correct sequence of operations is

A meter having 0-1000 A range and 1000 &amp;ohm; resistance is required to be changed to 0-100 mA meter. The value of shunt resistance is about

When measuring phase angle between two waves using a CRO, the time base generator is connected to

Two voltmeters 0-250 V each having resistances of 5 k&amp;ohm; and 10 k&amp;ohm; respectively and are connected in series. To ensure that neither of them goes beyond scale the total voltage which can be applied should be less than

A 24 mm long conductor has a resistance of 128 &amp;ohm;. The change in resistance is 13.3 &amp;ohm; and change in length is 1.6 mm under tension. The gauge factor is

A meter has a square law scale. For 2 A current the deflection in 90 . For a deflection of 45 , the current is

Measuring of unknown voltage with a dc potentiometer loses its advantage of open circuit measurement when

It is required that a strain gauge has gauge factor of 100. The proper strain gauge is

Assertion (A): Metals are better heat conductors than insulators.Reason (R): If is temperature gradient, Q is heat flow density and K is thermal conductivity, then Q = - K (dT/dx).

In a polyatomic gas, the types of polarization which exist together are

At T = 0, the resistivity of a perfect single crystal of a metal is

In figure, the position of voltmeter and ammeter are exchanged. It may result in damage to

Lines of magnetic field cannot intersect.

The volt ratio box is basically a

A sinusoidal ac voltage of amplitude 100 V is applied to a rectifying device which offers 10 &amp;ohm; resistance in forward direction and infinite resistance in backward direction. A moving coil ammeter is also connected in the circuit. The reading of ammeter will be

A variable reluctance tachometer has 180 teeth on rotor. The speed of shaft on which it is mounted in 1200 rpm. The frequency of output pulses is

The number of tightly bound electrons in silicon atom are

The iron core of a coil is removed so that it becomes an air cored coil. Its inductance will

A circular sphere mile is the area of cross-section of a wire

In an hydrogen atom, an electron moves in the field of a proton. The stability of orbit requires equilibrium between coulomb's force and centrifugal force.

A particle of charge Q coulombs is bound elastically to an equilibrium position with a force constant of f newton per metre. The polarizability of the system is

1 Bohr magneton = .

The orientation polarization of a polyatomic gas is inversely proportional to absolute temperature.

For small size high frequency coils, the most common core material is

In a virgin specimen of iron, the direction of spontaneous magnetisation varies from domain to domain.

Which of the following is used in lightning arresters?

High frequency inductors and capacitors are commonly plated with silver. The main purpose of this is to

In its lowest state, the electron is bound to the field of proton by an energy equal to

In a ferromagnetic material, the internal field seen by a dipole is

An induction wattmeter can be used for

A meter having 0-1000 A range and 1000 &ohm; resistance is required to be changed to 0-100 mA meter. The value of shunt resistance is about

Two voltmeters 0-250 V each having resistances of 5 k&ohm; and 10 k&ohm; respectively and are connected in series. To ensure that neither of them goes beyond scale the total voltage which can be applied should be less than

A 24 mm long conductor has a resistance of 128 &ohm;. The change in resistance is 13.3 &ohm; and change in length is 1.6 mm under tension. The gauge factor is

A sinusoidal ac voltage of amplitude 100 V is applied to a rectifying device which offers 10 &ohm; resistance in forward direction and infinite resistance in backward direction. A moving coil ammeter is also connected in the circuit. The reading of ammeter will be