Top 50 Basic Electronics MCQ Part -2

This post contains Top 50 Basic Electronics MCQ. If you want to see my previous post on basic electronic part – 1 click here.

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Top 50 basic electronics multiple choice questions MCQ

For detail explanation of all question please check video at end of this page.

Top 50 Questions and Answer

Question 1 Choose the below option in terms of ascending order of band gap energy

• Diamond, Graphite, Silicon
• Graphite, Silicon, Diamond
• Silicon, Graphite, Diamond
• Silicon, Diamond, Graphite

Answer: Graphite, Silicon, Diamond

Question 2 Carrier lifetime for holes and electrons in a semiconductor ranges from

• Milliseconds to hundreds of nanoseconds
• Microseconds to seconds
• Nanoseconds to hundreds of microseconds
• Nanoseconds to thousands of milliseconds

Answer: Nanoseconds to hundreds of microseconds

Explanation

For an intrinsic semiconductor with equal concentration of holes and electron, the carrier lifetime for free electrons and holes is determined by the rate of recombination. While new electron-hole pairs are formed due to thermal agitation, existing electron-hole pair disappear due to recombination.

Question 3 Choose the below option in terms of ascending order of band gap energy

• Conduction and Diffusion
• Conduction
• Diffusion
• None of the above

Answer: Conduction and Diffusion

Explanation

Two ways in which charge carriers are transferred in semiconductor are – conduction and diffusion

Conduction in semiconductor is accomplished by movement of free electrons and holes. While electrons are negative charge carrying particles, holes are positive charge carrying particles. Both their current is in same direction.

Diffusion is caused by movement of charge carriers from higher concentration area to lower concentration area. This is possible because of non-uniform concentration in semiconductors.

Question 4 The thickness of space charge region for a P-N junction diode is of the order of

• 10-4 cm
• 10-2 cm
• 10 cm
• 100 cm

Answer: 10-4 cm

Explanation

For a P-N junction diode, the space charge region is the region devoid of mobile charge carriers near to the junction. The electro-static potential variation in this region forms a potential barrier which opposes further diffusion of opposite charge carriers across the junction.

Question 5 Formation of a junction between a sample of P-type and N-type material causes _______ action

• Rectifying
• Conducting
• Insulating
• None of the above

Answer: Rectifying

Explanation

Addition of donor atoms into one side of an intrinsic semiconductor (like Germanium) and acceptor atoms into another side, causes formation of a junction. Under no external applied electric field, a potential barrier exists across the junction due to formation of depletion region (depletion of mobile charge carriers). However, when an external electric field is applied such that p-region is of positive polarity and n-region is of negative polarity, the potential barrier is reduced, causing flow of current. This is called Forward biasing.

When the opposite occurs, i.e. p-region is of negative polarity and n-region is of positive polarity, the potential barrier is increased, hindering the flow of current. Thus,  since the p-n junction device would allow flow of electricity in only one half of the electric signal, but not in the other half, this constitutes rectifying action.

Question 6 Cut-In or breakdown voltage of Silicon diode is greater than that of Germanium diode because ______.

• Reverse saturation current in a Silicon diode is lesser than that in Germanium diode
• Reverse saturation current in Germanium diode is lesser than that in Silicon diode
• The current is initially less dependent on voltage for a Silicon diode
• None of the above

Answer: Reverse saturation current in a Silicon diode is lesser than that in Germanium diode and The current is initially less dependent on voltage for a Silicon diode

Explanation

For a Germanium diode, the breakdown voltage is about 0.2 V, whereas that of Silicon diode is 0.6 Volts. The reason being that, reverse saturation current in a Ge diode is about 1000 times more than that in Si diode. Also, current flowing through the diode is as given below;

I = Io ( e V/ηVT  – 1 )

For Ge, the symbol  η = 1, whereas that for Si is 2 for small currents and 1 for large currents. Hence, for first several tenths of volts, the current varies as e V/2VT.

Question 7 The d.c. resistance of a crystal diode is ………….. its a.c. resistance

• The same as
• More than
• Less than
• None of the above

Answer: Less than

Explanation

• In the Crystal equivalent Circuit there is an Inductor [ L]& Capacitor [C] are series. The value of these L, C impedance varies with frequency and at resonance this cancels and only R – resistance is available which is equivalent to the DC Value.
• The impedance values of L & C changes in opposite directions at all other frequencies other than resonance and hence the AC Resistance is more .
• Therefore, the conclusion is DC resistance is less .

Question 8 A crystal diode is used as ……………

• an amplifier
• a rectifier
• an oscillator
• a voltage regulator

Answer: a rectifier

Explanation

The crystal diode can be used as a rectifier to convert the AC into DC. As it conducts only in one direction and blocks the current flow in the reverse direction as similar to the normal diode– it can be used to design the half wave, full wave and bridge rectifier circuits.

Question 9 Question 9 Band gap Energy for Silicon and Germanium at Room Temperature (300°K) are ____ & ____ respectively

• 56eV, 1.1eV
• 72eV, 1.2eV
• 1eV, 0.72eV
• 1eV, 0.56eV

Answer: 1eV, 0.72eV

Explanation

Below are the band gap energy relations with temperature for both Silicon and Germanium

Egsi (T) = 1.21 – 3.60 x 10-4

Egge (T) = 0.785 – 2.23 x 10-4

Substituting T = 300 in both the above equations, we get Bandgap energies as given below;

Egsi (300) = 1.1 eV

Egge (300) = 0.72 eV

Question 10 Depletion layer in semiconductor diode is caused by

• Doping
• Recombination
• Barrier potential
• Ions

Answer: Recombination

Explanation

The depletion region is cause by the diffusion of charges. Because of the concentration gradient holes diffuse from p-side to the n-side across the junction while electrons diffuse from the n-side to the p-side. The holes and the electrons diffusing towards each other combine near the junction. In doing so positive and negative ions are formed. The pair of positive and negative ions at the junction forms the dipole. The region containing the dipoles and completely depleted of mobile charge is called the depletion region

Question 11 Zener diode can be described as

• A rectifier diode.
• A device with constant – voltage.
• A device with constant – current.
• A device that works in the forward region.

Answer: A device with constant – voltage.

Explanation

• A Zener diode is a heavily doped semiconductor device that is designed to operate in the reverse direction.
• A Zener diodeis a silicon semiconductor devicethat permits current to flow in either a forward or reverse direction. … Additionally, the voltage drop across the diode remains constant over a wide range of voltages, a feature that makes Zener diodes suitable for use in voltage regulation

Question 12 Voltage multipliers produce

• Low voltage and low current
• Low voltage and high current
• High voltage and low current
• High voltage and high current

Answer: High voltage and low current

Explanation

A voltage multiplier is a specialized rectifier circuit producing an output which is theoretically an integer times the AC peak input, for example, 2, 3, or 4 times the AC peak input. Thus, it is possible to get 200 VDC from a 100 Vpeak AC source using a doubler, 400 VDC from a quadrupler. Any load in a practical circuit will lower these voltages.

Question 13 A Diode is a

• Bilateral Device
• Nonlinear Device
• Linear Device
• Unipolar Device

Answer: Linear Device

Explanation

Diode is a Non Linear Device. Its just an electronic switch which turns on during forward bias and off during reverese bias. … A linear device is that whose output is directly propostional to input. In case of diode, output (i.e current) is not directly propostional to it input(i.e voltage across it).

Question 14 What is a Clamper?

• A circuit that adds a DC voltage (positive or negative) to a wave
• A circuit that adds a AC voltage (positive or negative) to a wave
• A circuit that removes a part (positive or negative) of a waveform 
• All of the above

Answer: A circuit that adds a DC voltage (positive or negative) to a wave

Explanation

A clamper is an electronic circuit that changes the DC level of a signal to the desired level without changing the shape of the applied signal.

In other words, the clamper circuit moves the whole signal up or down to set either the positive peak or negative peak of the signal at the desired level.

Question 15 What is a Clipper?

• circuit that adds a DC voltage (positive or negative) to a wave
• A circuit that adds a AC voltage (positive or negative) to a wave
• A circuit that removes a part (positive or negative) of a waveform 
• All of the above

Answer: A circuit that removes a part (positive or negative) of a waveform 

Explanation

A clipper is a device which limits, remove or prevents some portion of the wave form (input signal voltage) above or below a certain level In other words the circuit which limits positive or negative amplitude ,or both is called chipping circuit.

Question 16 The reverse saturation current in a Silicon Diode is _____ than that of Germanium Diode

• Equal
• Higher
• Lower
• Depends on temperature

Answer: Lower 

• In germanium diodes, a small increase in temperature generates large number of minority charge carriers.
• The number of minority charge carriers generated in the germanium diodesis greater thanthe silicon diodes. Hence, the reverse saturation current in the germanium diodes is greater than the silicon diodes.

Question 17 The forward voltage drop across a silicon diode is about ……

• 2.5 V
• 3 V
• 10 V
• 0.7 V

Answer: 0.7 V

Question 18 A zener diode has ………..

• one pn junction
• two pn junctions
• three pn junctions
• none of the above

Answer: one pn junction

Question 19  A zener diode is used as …………….

• an amplifier
• a voltage regulator
• a rectifier
• a multivibrator

Answer: a voltage regulator

Question 20 A zener diode is always ………… connected.

• reverse
• forward
• either reverse or forward
• none of the above

Answer: reverse

Explanation

• A Zener diode is always reverse connected
• When forward biased, its characteristics are just like of ordinary diode
• It has sharp breakdown voltage, called Zener voltage

Question 21 A zener diode utilizes ……….. characteristics for its operation.

• forward
• reverse
• both forward and reverse
• none of the above

Answer: reverse

Question 22 A zener diode has ………….. breakdown voltage.

• undefined
• sharp
• zero
• none of the above

Answer: sharp

Explanation

• A Zener diode is always reverse connected
• When forward biased, its characteristics are just like of ordinary diode
• It has sharp breakdown voltage, called Zener voltage

Question 23 A zener diode is …………………. device

• a non-linear
• a linear
• an amplifying
• none of the above

Answer: a non-linear

Explanation

• A Zener diode is always reverse connected
• When forward biased, its characteristics are just like of ordinary diode
• It has sharp breakdown voltage, called Zener voltage

Question 24  ………. rectifier has the lowest forward resistance.

• solid state
• vacuum tube
• gas tube
• none of the above

Answer: solid state

Question 25 A series resistance is connected in the zener circuit to………...

• properly reverse bias the zener
• protect the zener
• properly forward bias the zener
• none of the above

Answer: protect the zener

Question 26 The disadvantage of a half-wave rectifier is that the…….

• components are expensive
• diodes must have a higher power rating
• output is difficult to filter
• none of the above

Answer: output is difficult to filter

Explanation

• They only allow a half-cycle through per sinewave, and the other half-cycle is wasted. This leads to power loss.
• They produces a low output voltage.
• The output current we obtain is not purely DC, and it still contains a lot of ripple (i.e. it has a high ripple factor)

Question 27 The Hall effect is used to determine the

• Only the carrier concentration of semiconductors
• Current flowing across a semiconductor
• Type of semiconductor and carrier concentration
• None of the above

Answer: Type of semiconductor and carrier concentration

Explanation

Hall effect is the phenomenon of induction of electric field in a semiconductor specimen carrying current of magnitude I, when placed in a transverse magnetic field, B. If current is in positive X direction, Magnetic field is in positive Z direction, force will be exerted in negative Y direction. The polarity of voltage, VH across the specimen determines whether it is N-type or P-type.

Also, carrier concentration is determined as:

n (p) = ρ/e, where ρ = charge density and e is magnitude of charge

Now, ρ = 1/RH,, where RH is Hall coefficient and is given as: RH = VHw/BI

w = width of the specimen in direction of magnetic field.

Question 28 The ripple factor of a half-wave rectifier is …………………

• 2
• 1.21
• 2.5
• 0.4

Answer: 1.21

Question 29 For the same secondary voltage, the output voltage from a center-tap rectifier is ………… than that of bridge rectifier

• twice
• thrice
• four time
• one-half

Answer: one-half

Question 30 There is a need of transformer for ………………..

• half-wave rectifier
• Centre-tap full-wave rectifier
• bridge full-wave rectifier
• none of the above

Answer: Centre-tap full-wave rectifier

Question 31 For the same secondary voltage, the output voltage from a centre-tap rectifier is ………… than that of bridge rectifier

• twice
• thrice
• four time
• one-half

Answer: one-half

Question 32 The PIV rating of each diode in a bridge rectifier is ……………… that of the equivalent centre-tap rectifier

• one-half
• the same as
• twice
• four times

Answer: one-half

Explanation

Peak inverse voltage(PIV) or peak reverse voltage(PRV) can be defined as the maximum value of the reverse voltage of a diode, which occurs at the peak of the input cycle when the diode is in reverse bias.

The PIV of bridge rectifiers is = Vm

The PIV of Center taped rectifiers is= 2Vm

The PIV (peak inverse voltage) ratings of the diodes in bridge rectifier is half than that of needed in a center tapped full wave rectifiers.

Question 33 A 10 V power supply would use …………………. as filter capacitor.

• paper capacitor
• mica capacitor
• electrolytic capacitor
• air capacitor

Answer: electrolytic capacitor

Question 34 A 1,000 V power supply would use ……….. as a filter capacitor

• paper capacitor
• air capacitor
• mica capacitor
• electrolytic capacitor

Answer: paper capacitor

Question 35 The most widely used rectifier is ……………….

• half-wave rectifier
• centre-tap full-wave rectifier
• bridge full-wave rectifier
• none of the above

Answer: bridge full-wave rectifier

Explanation

Advantages

• The efficiency of the bridge rectifier is higher than the efficiency of a half-wave rectifier. …
• The DC output signal of the bridge rectifier is smoother than the output DC signal of a half-wave rectifier.
• In a half-wave rectifier, only half of the input AC signal is used and the other half is blocked.

Question 36 The maximum efficiency of a half-wave rectifier is ………………..

• 40.6 %
• 81.2 %
• 50 %
• 25 %

Answer: 40.6%

Question 37 The ……………….. filter circuit results in the best voltage regulation

• choke input
• capacitor input
• resistance input
• none of the above

Answer: choke input

Question 38 A register with color bands: Yellow-Violet-Red, gold, has the value:

• 47k 5%
• 4k7 5%
• 470R 5%
• 47R 5%

Answer: 4k7 5%

Explanation

Digit, Digit, Multiplier = Colour, Colour x 10 colour  in Ohm’s (Ω)

For example, a resistor has the following coloured markings;

Yellow Violet Red = 4 7 2 = 4 7 x 102 = 4700Ω or 4k7 Ohm.

Question 39 The voltage out of an ideal voltage source is

• Zero
• Constant
• Load resistance dependent
• Internal resistance dependent

Answer: Constant

Explanation

An ideal voltage source has the following characterstic that allows it to act as a 100% efficient source of voltage: it has zero internal resistance. When an ideal voltage source has zero internal resistance, it can drop all of its voltage perfectly across a load in a circuit.

Question 40 The voltage out of an ideal current source is

• Zero
• Constant
• Load resistance dependent
• Internal resistance dependent

Answer: Constant

Explanation

An ideal current source generates a current that is independent of the voltage changes across it.

Question 41 The path between two points along which an electrical current can be carried is called

• A network
• A relay
• A circuit
• A loop

Answer: A circuit

Question 42 If the Zener Diode is connected in wrong polarity, the voltage across the load is

• 0.7 V
• 10 V
• 14 V
• 18 V

Answer: 0.7V

Question 43 What is the tolerance of a resistor having sliver tolerance band

• 10%
• 5%
• 20%
• 2%

Answer: 10%

Question 44 PCB stands  for

• Proper circuit board
• Printed circuit board
• Printed circle board
• Printed circuit bond

Answer: Printed circuit board

Question 45 The chemical compound used for etching of PCB is

• Ferrous sulphate
• Ferric chloride
• Copper sulphate
• None of the above

Answer: Ferric chloride

Question 46 The specified deviation in the resistant value of a resister is called

• Capacitance
• Tolerance
• Inductance
• Color code

Answer: Tolerance

Explanation

This specified deviation is called ‘tolerance’. Every resistor has a specified tolerance range over which the resistance value is allowed to vary; anywhere from approximately 0.1% to 20% of the nominal value.

Question 47 Material classified as good conductors of electricity if

• The conduction and valence bands overlap
• There is a narrow forbidden, energy gap
• There is a wide forbidden, energy gap
• None of the above

Answer: The conduction and valence bands overlap

Question 48  ——- is an electronics component that opposes the flow of current

• Capacitor
• Resistor
• Inductor
• None of the above

Answer: Resistor

Question 49 A resistors has the following color bands- yellow, violet, orange, silver. Its value will be

• 4.7 = 10%
• 47 + 5%
• 47k + 10%
• None of the above

Answer: 47k + 10%

Question 50 The number of holes in an intrinsic semiconductor is

• Equal to number of free electrons
• Greater than number of free electrons
• Less than number of free electrons
• None of the above

Answer: Equal to number of free electrons

Click here to download top 50 basic electronics MCQ’s pdf file.

I have explained all questions in this video. pdf of these question check at the end.