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# Electronics - Most Important MCQs With Explanation

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QUESTION:

The basic purpose of filter is to?

A.

Minimize variation in ac signal

B.

Suppress hannonics in rectified output

C.

Remove ripples from the rectified output

D.

Stabilize dc output voltage

EXPLANATION

A filter circuit is a device that removes the a.c. component of rectifier output and allows only d.c. component to reach the load.

QUESTION:

Non-inverting amplifier circuits have?

A.

A very high input impedance

B.

A very low input impedance

C.

A low output impedance

D.

None of the above options is correct

EXPLANATION

Operational amplifiers have high input impedance and low output impedance because of the concept of a voltage divider, which is how voltage is divided in a circuit depending on the amount of impedance present in given parts of a circuit. Operational amplifiers are voltage-gain devices.

QUESTION:

The electron volt is the unit of __________.

A.

Electric current

B.

Electric potential

C.

Electric energy

D.

Electric flux

EXPLANATION

An electron volt is a unit of electric energy equal to the work done on an electron in accelerating it through a potential difference of one volt. Other units of electric energy are erg and Joules.

QUESTION:

The open-circuit test in a transformer is used to measure?

A.

Copper loss

B.

Winding loss

C.

Total loss

D.

Core loss

EXPLANATION

The open-circuit test is done to find the core loss of the transformer. It is done by keeping one of the windings open (without load, usually the high voltage winding is open) and applying rated voltage to the other winding (usually the low voltage winding because it is easier to apply rated voltage).

QUESTION:

Full wave rectifier uses:

A.

One diode

B.

Two diodes

C.

Three diodes

D.

Four diodes

EXPLANATION

This is a standard answer. You can make a half-wave rectifier with one diode. For a full-wave bridge rectifier, you will need four diodes.

QUESTION:

Consider a peak rectifier fed by a 60-Hz sinusoid having a peak value Vp = 100V. Let the load resistance R = 10kΩ . Calculate the fraction of the cycle during which the diode is conducting:

A.

1.06 %

B.

2.06 %

C.

3.18 %

D.

4.82 %

EXPLANATION

The correct answer is Option C: 3.18 %

The best I can explain: w Δt ~ √(2Vr/Vp)

Θ = √(2 X 2/100)

Θ = 0.2 rad or 3.18 % of the cycle.

QUESTION:

Which two or more of the following actions would increase the energy stored in a parallel plate capacitor when a constant potential difference is applied across the plates:

A.

Decreasing the area of the plates & decreasing the separation between the plates

B.

Decreasing the area of the plates & increasing the separation between the plates & inserting a dielectric between the plates

C.

Increasing the area of the plates & decreasing the separation between the plates & inserting a dielectric between the plates

D.

Increasing the area of the plates & increasing the separation between the plates

EXPLANATION

The energy stored by a parallel plate capacitor depends upon the area of the plates, the distance between the plates, and the presence of dielectric between the plates. The energy stored will increase by increasing the Aaea of the plates, decreasing the distance between them, and by placing a dielectric between the plates.

QUESTION:

To get a peak load voltage of 40V out of a bridge rectifier, what should be the approximate rms value of secondary voltage?

A.

0 V

B.

14.4 V

C.

28.3 V

D.

56.6 V

EXPLANATION

Following is the solution to this question:

QUESTION:

A cable 4 km long and of total resistance 1 Ohm carries electric current from a generator producing 100kW at 10,000 Volts. The current in amperes in the cable is:

A.

10

B.

10,000

C.

1000

D.

100,000

EXPLANATION

The explanation for this question is given below:

QUESTION:

In full wave rectifier with input frequency 50 Hz the ripple in the output is mainly of frequency

A.

25 Hz

B.

50Hz

C.

100 Hz

D.

Zero

EXPLANATION

In full-wave rectification, ripple frequency is twice the input frequency whereas for half-wave rectifiers it is equal to the AC supply frequency.

QUESTION:

In half-wave rectification, the output DC voltage is obtained across the load for ______.

A.

The positive half cycle of input AC

B.

The negative half cycle of input AC

C.

The positive and negative half cycles of input AC

D.

Either positive or negative half cycle of input

EXPLANATION

In half-wave rectification, the output DC voltage is obtained across the load for either the positive or negative half cycle of input.

QUESTION:

If peak voltage across a full wave rectifier is 20V then Vrms is:

A.

7.07v

B.

14.14v

C.

16.8v

D.

12v

EXPLANATION

In a full-wave rectifier, the relationship between peak voltage and the rms(root mean square) is VP = 2 V rms. V rms here is unknown, peak voltage is 20V, which, when divided by the square root of 2, gives us V rms which is roughly 14.14 V.

QUESTION:

In full wave rectifier with input frequency 50 Hz, the ripple in the output is mainly of frequency?

A.

25 Hz

B.

50 Hz

C.

100 Hz

D.

Zero

EXPLANATION

The rectifier rectifies both positive and negative sides of the waveforms, doubling the input frequency and giving 100Hz as the output.

QUESTION:

Transistors can be used as:

A.

Half wave rectifier

B.

Full wave rectifier

C.

Both

D.

None of these

EXPLANATION

Transistors, if their base-emitter or base-collector regions are connected, can function as either a full or half wave rectifier.

QUESTION:

In half wave rectification, the output DC voltage is obtained across the load for?

A.

The positive half cycle of input AC

B.

The negative half cycle of input AC

C.

The positive and negative half cycles of input AC

D.

Either positive or negative half cycle of input AC

EXPLANATION

A half wave rectifier would rectify either positive or negative, not both, hence the output Voltage would be corresponding to the input AC voltage of one of the two polarities.

QUESTION:

A diode works in ___ bias for rectification.

A.

Forward

B.

Reverse

C.

Mid

D.

Positive

EXPLANATION

When the AC voltage is positive on the cathode side of the diode, the diode allows the current to pass through to the output. But when the AC current reverses direction and becomes negative on the cathode side of the diode, the diode blocks the current so that no voltage appears at the output. Under reverse bias, minority carriers free electrons in the p-type semiconductor and the minority carriers holes in the n-type semiconductor start flowing across the junction. Thus, electric current is produced in the reverse bias diode due to the minority carriers. However, the electric current produced by the minority carriers is very small. So, the minority carrier current in the reverse bias condition is neglected.

QUESTION:

Maximum efficiency of half wave rectifier is:

A.

80.6 %

B.

40.6 %

C.

70%

D.

50%

EXPLANATION

Half-wave rectifiers have a large ripple factor and make use of only one half-cycle of the input. Unlike full-wave rectifiers, they don’t even use transformers, so they have a much lower efficiency (half that of a full-wave rectifier).

QUESTION:

In a centre tap full wave rectifier if Vm is the peak voltage across the secondary of transformer, the maximum voltage across reverse bias is

A.

Vm

B.

Vm/v2

C.

2Vm

D.

Vm/3

EXPLANATION

Using the concept of Peak Inverse Voltage, it can be found that if the input peak voltage is Vm, the Peak Inverse Voltage is 2 times that, hence 2Vm

QUESTION:

Gamma rays are attracted towards

A.

Negative plate

B.

Positive plate

C.

No deflection

D.

Pass through the medium

EXPLANATION

Gamma rays have no charge, hence 0 deflection, but also their penetrating power allows them to simply pass through most mediums without blockage.

QUESTION:

Which of the following is not a type of rectifier?

A.

Phase wave rectifier

B.

Full wave

C.

halfwave

D.

none of them

EXPLANATION

The two main types of rectifiers are Half Wave & Full Wave rectifiers. Phase Wave is not a type of rectifier. Hence option A is correct.

QUESTION:

Half wave voltage multiplier can provide any degree of voltage multiplication by cascading diodes and capacitors.

A.

any doubler

B.

any tripler

C.

any multiplication

D.

none of them

EXPLANATION

Half wave voltage multipliers can provide any degree of multiplication of the input voltage by cascading diodes and capacitors. Hence option C is correct.

QUESTION:

A half-wave rectifier uses:

A.

One diode

B.

Two diodes

C.

Three diodes

D.

Four diodes

EXPLANATION

This is a fact to be memorized. A half-wave rectifier circuit employs only one diode to generate a Half-Wave Rectified Output. Hence A is the correct answer.

QUESTION:

Which of the following rectifier uses a wheatstone bridge to rectify signals?

A.

Half wave

B.

Full wave

C.

Bridge

D.

All of the above options are correct

EXPLANATION

This is a fact to be memorized. All bridge rectifiers are a type of Wheatstone Bridge circuits. Hence C is the correct answer.

QUESTION:

Consider a peak rectifier fed by a 60-Hz sinusoid having a peak value Vp = 100 V. Let the load resistance R = 10 kΩ. Calculate the fraction of the cycle during which the diode is conducting:

A.

1.06 %

B.

2.06 %

C.

3.18 %

D.

4.82 %

EXPLANATION

w Δt ~ √(2Vr/Vp)

= √(2 X 2/100)

= 0.2 rad or 3.18 % of the cycle.

QUESTION:

The process of converting alternating current to direct current is called?

A.

Modulation.

B.

Amplification.

C.

Oscillation.

D.

Rectification.

EXPLANATION

A rectifier converts alternating current to direct current and this process of converting AC to DC is known as rectification.

QUESTION:

The ripple factor of half-wave rectifier is?

A.

1.21.

B.

0.8.

C.

0.6.

D.

0.4.

EXPLANATION

Ripple factor determines how well a half-wave rectifier can convert AC voltage to DC voltage. The ripple factor of a half-wave rectifier is 1.21.

QUESTION:

A full wave rectifier uses load resistor of 1500 Ω. Assume the diodes have Rf= 10 Ω, Rr= ∞. The voltage applied to diode is 30V with a frequency of S0Hz. Calculate the AC power input.

A.

358.98mW.

B.

275.2mW.

C.

145.76 mW.

D.

456.78 mW.

EXPLANATION

The AC power input; PIN=IRMS2(RF+Rr).

IRMS= Im/√2 = Vm/(Rf+RL)√2 = 30/[(1500+10) x 1.414] = 13.5mA.

So, PIN= (13.5 x 10-3)2 x (1500+10) =275.2mW.

QUESTION:

Which of the following is a type of rectifier?

A.

Half wave

B.

Full wave

C.

Bridge

D.

All of the above options are correct

EXPLANATION

A half-wave rectifier is defined as a type of rectifier that allows only one-half cycle of an AC voltage waveform to pass while blocking the other half cycle.

A full-wave rectification rectifies the negative component of the input voltage to a positive voltage, then converts it into DC (pulse current).

A bridge rectifier is a type of full-wave rectifier that uses four or more diodes in a bridge circuit configuration to efficiently convert alternating (AC) current to a direct (DC) current.

Hence, all of the above options are types of rectifiers.

QUESTION:

If a half-wave rectifier is used to convert 50Hz AC into DC, then the number of pulses present in the rectifier voltage is:

A.

25

B.

50

C.

100

D.

75

EXPLANATION

Rectifiers produce uni-directional and pulsating voltage from an AC source. The number of pulses per second in the rectified voltage is the same as that of the input voltage, since the input voltage is 50 Hz then the pulses per second are also 50.

QUESTION:

Transformer is used in rectification to ________ the supply voltage.

A.

Step up

B.

Step down

C.

Equalize

D.

None of these options is correct

EXPLANATION

Transformers are used in rectification to step down the supply voltage as during rectification we use a transformer to get AC supply and receive a very high voltage of 240V, which can damage or burn out components like diodes, transistors etc. Therefore, transformers are used to convert the voltage into a lower value to protect the components from damage.

QUESTION:

A full wave rectifier uses a load resistor of 15000. Assume the diodes have RF=l0 Ohms and Rr= infinite. The voltage applied to the diodes is 30V with a frequency of 50Hz. Calculate the AC power input.

A.

358.98 mW

B.

275.2 mW

C.

145.76 mW

D.

456.78 mW

EXPLANATION

The AC power input PIN=IRMS2(RF+Rr).

I(RMS)=Im/√2 = Vm/(RF+RL)√2 = 30/(1500+10) x 1.414 = 13.5mA

So, PIN=(13.5 x 10-3)2 x (1500+10) = 275.2 mW.

QUESTION:

The sun gives light at the rate of 1500 W/m2 of area perpendicular to the direction of light. Assume the wavelength of light as 5000 Å. Calculate the number of photons/s arriving at 1 m2 area at that part of the earth.

A.

4.770 x 1021

B.

3.770 x 1011

C.

3. 770 x 102

D.

3.770 x 1022

EXPLANATION

Given that,

I = 1500 W/m²

λ = 5000 Å

Energy of a particle of light (E), called a photon, is proportional to its frequency (f), by a constant factor (h) which is called the Plank’s constant with a value of 6.626 x 10-34 kgm²/s.

Giving the equation, E=hv

E = hc/λ

Speed of light = v = 3x108 m/s,

Number of photons received = n = IA/E

n = IA/hv

n = (1500 x 1)(5000 x 10-10) /(6.626 x 10-34 )(3 x 108)

n = 3.77 x 1021

QUESTION:

Most widely used rectifier is:

A.

half wave rectifier

B.

full wave rectifier

C.

bridge rectifier

D.

none of them

EXPLANATION

Bridge rectifier is the most commonly used rectifier in electronics.

QUESTION:

Transistors can be:

A.

half wave rectifier

B.

full wave rectifier

C.

both

D.

none

EXPLANATION

Transistor can be used as a switch for opening and closing of the circuit. A transistor can also act as an amplifier, but not rectifier Since none of these answers are in the options, the answer is D.

QUESTION:

A full wave rectifier uses load resistor of 1500 ohm. Assume the diodes have Rf = 10 ohm, Rr = infinity. The voltage applied to diode is 30V with a frequency of 50Hz. calculate AC power input.

A.

358.98 mW

B.

275.2 mW

C.

145.76 mW

D.

456.78 mW

EXPLANATION

The AC P(in)=Irms^2(RF+Rr).

Irms=Vm/(Rf+RL)√2

=30/(1500+10) x 1.414

=13.5mA

So, P(in)=(13.5 x 10^-3)^2 x (1500+10)=275.2mW.

QUESTION:

In half-wave rectification, during negative cycle of the wave, the diode is:

A.

Reverse biased

B.

Forward biased

C.

Potential barrier

D.

None of these options are correct

EXPLANATION

During the positive half cycle of the AC voltage, the diode will be forward biased and the current flows through the diode. During the negative half cycle of the AC voltage, the diode will be reverse biased and the flow of current will be blocked. So the correct option is A.

QUESTION:

The ripple factor of full-wave rectifier is:

A.

1.21

B.

0.6

C.

0.482

D.

0.9

EXPLANATION

The ripple factor for a full-wave rectifier is 0.482 which can also be written as 48.2%.

QUESTION:

The number of diodes in bridge rectifier is:

A.

4

B.

3

C.

2

D.

5

EXPLANATION

Bridge rectifiers use four diodes that are arranged cleverly to convert the AC supply voltage to a DC supply voltage. Hence the correct option is A.

QUESTION:

The ripple factor of a half-wave rectifier is:

A.

1.21

B.

0.8

C.

0.6

D.

0.4

EXPLANATION

The ripple factor of a half-wave rectifier is 1.21.

QUESTION:

A full-wave rectifier is operating from 50 Hz. The fundamental frequency of the ripple will be:

A.

100 Hz

B.

25 Hz

C.

50 Hz

D.

200 Hz

EXPLANATION

A full-wave rectifier rectifies both the half cycles of the AC input meaning it conducts twice during a cycle. The output frequency is double to that of the input frequency.

The output frequency of a full-wave rectifier is 2 x 50 = 100 Hz.

QUESTION:

Half-wave rectifier has _____ diodes.

A.

1

B.

2

C.

3

D.

4

EXPLANATION

A half-wave rectification is where an alternating voltage of a certain period (input voltage) is applied to a single diode which is connected in series with a load resistance.

QUESTION:

The number of diodes in a bridge rectifier is:

A.

5

B.

4

C.

3

D.

2

EXPLANATION

Bridge Rectifiers use four diodes that are arranged cleverly to convert the AC supply voltage to a DC supply voltage. Hence the correct option is A.

QUESTION:

Rectifier is a device which converts?

A.

AC to DC

B.

DC to AC

C.

AC to triangular current

D.

DC to triangular current

EXPLANATION

Rectifiers convert the current from AC to DC. AC is current that switches between flowing backwards and forwards at regular intervals while DC flows in a single direction.

QUESTION:

The bridge rectifier is preferred to an ordinary two diode full wave rectifier because:

A.

It needs much smaller transformer for the same output

B.

No center tap required

C.

Less PIV rating per diode

D.

All of the above

EXPLANATION

For high voltage applications, a bridge rectifier is preferred because of the low PIV rating per diode. It can be constructed with or without a transformer and it does not require a center tap transformer.

QUESTION:

Ripple factor is defined as?

A.

lrms/Vrms

B.

ldc/lrms

C.

lrms/I dc

D.

lrms +Idc

EXPLANATION

The ripple factor is defined as the ratio of the rms value of the ac component to the dc component.

QUESTION:

If a half wave rectifier is used to convert 50Hz AC into DC, then the number of pulses present in rectifier voltage is?

A.

25

B.

50

C.

100

D.

75

EXPLANATION

50 Hz means that current or voltage will change its direction from + to – 50 times in 1 second so it will complete 50 cycles per second. After rectification, the negative half of the cycle will get erased. So for that part of the cycle, the voltage will remain to be Zero.

There’s no effect on the cycle length. Hence the number of pulses before and after rectification will remain the same in half-wave rectification.

QUESTION:

The process of converting alternating current into direct current is called:

A.

Modulation

B.

Amplification

C.

Ossilation

D.

Rectification

EXPLANATION

The process of converting alternating current and voltage into direct current and voltage is called rectification.

This is used in electronic equipment which requires a direct current. For example, voltage in many devices must be rectified from the alternating voltage produced at power stations.

QUESTION:

In half wave rectification, the output DC voltage is obtained across the load for

A.

The positive half cycle of input AC

B.

The negative half cycle of input AC

C.

The positive and negative half cycles of input AC

D.

Either positive or negative half cycle of input AC

EXPLANATION

The DC current or DC voltage produced by the negative half wave rectifier is measured across the load resistor RL. The output DC current or DC signal produced by a negative half wave rectifier is a series of negative half cycles or negative sinusoidal pulses.

QUESTION:

To get a peak load voltage of 40V out of a bridge rectifier, what should be the approximate rms value of secondary voltage?

A.

0V

B.

14.4V

C.

28.3V

D.

56.6V

EXPLANATION

Vm = 40V

Vrms = (Vm / √2) = (40 / √2) = 28.28V

∴ To get Vm of 40V at output, Vrms of secondary voltage has to be 28.28V

QUESTION:

Transformer is used in rectification to ___ the supply voltage.

A.

Step up

B.

Step down

C.

Equalize

D.

None of them

EXPLANATION

In half wave rectifier, we generally use a step-down transformer because the voltage needed for the diode is very small. Applying a large AC voltage without using transformer will permanently destroy the diode.

QUESTION:

Most widely used rectifier is ?

A.

Half wave rectifier

B.

Full wave rectifier

C.

Bridge rectifier

D.

None of them

EXPLANATION

The bridge rectifier consisting of four diodes enables full wave rectification without the need for a centre tapped transformer. The bridge rectifier is an electronic component that is widely used to provide full wave rectification and it is possibly the most widely used circuit for this application.

QUESTION:

A full wave rectifier passes _____ into positive cycles.

A.

Lower half cycle

B.

Upper half cycle

C.

Both cycles

D.

None of these

EXPLANATION

Full-wave rectification rectifies the negative component of the input voltage to a positive voltage, then converts it into DC (pulse current) utilizing a diode bridge configuration.

QUESTION:

A half-wave rectifier has ______ diodes.

A.

1

B.

3

C.

2

D.

4

EXPLANATION

Only one diode is needed in the half-wave rectifier. This diode limits the current flow in one direction which means that only half of the AC waveform can pass through the diode.

QUESTION:

The ripple factor of half-wave rectifier is ___.

A.

1.21

B.

0.8

C.

0.6

D.

0.4

EXPLANATION

The ripple factor of half wave rectifier is equal to 1.21 (this value should be memorized).

QUESTION:

Which principle is used in solar cells?

A.

Momentum

B.

Charge

C.

Mass

D.

All of these

EXPLANATION

The light energy is converted to electrical energy in solar cells, while momentum is conserved.

QUESTION:

Which of the following rectifier uses a wheatstone bridge to rectify the signal:

A.

Half wave

B.

Full wave

C.

Bridge

D.

All of the above options are correct

EXPLANATION

A bridge rectifier is formed by connecting four diodes in the form of a Wheatstone bridge. It also provides full-wave rectification. During the first half of the AC cycle, two diodes are forward biased and during the second half of the AC cycle, the other two diodes become forward biased.

QUESTION:

Consider a peak rectifier fed by a 60-Hz sinusoid having a peak value Vp = 100 V. Let the load resistance R = 10 kCl. Calculate the fraction of the cycle during which the diode is conducting.

A.

1.06 %

B.

2.06%

C.

3.18%

D.

4.82%

EXPLANATION

w Δt ~ √(2Vr/Vp)

= √(2 X 2/100)

= 3.18% of the cycle

QUESTION:

In a centre tap full wave rectifier, if Vm is the peak voltage across the secondary transformer, the maximum voltage across reverse bias is ____.

A.

Vm

B.

Vm/√2

C.

2Vm

D.

Vm/3

EXPLANATION

The maximum voltage across reverse bias is twice that of Vm so it is going to be 2Vm.

QUESTION:

Rectifier is a device which converts

A.

AC to DC

B.

DC to AC

C.

AC to triangular current

D.

DC to triangular current

EXPLANATION

Option A is correct. Rectifier uses diodes to convert AC to DC by either half wave or full wave rectification. Option B is wrong because that is called inversion.

QUESTION:

Half wave rectifier passes only

A.

Lower half cycle

B.

Upper half cycle

C.

Both cycles

D.

None of them

EXPLANATION

Option B is correct. Half wave rectification that only the first half cycle of the sinusoidal wave is passed.

Reference; https://www.electronics-tutorials.ws/wp-content/uploads/2013/08/diode39.gif?fit=450%2C153

QUESTION:

Ripple factor of full wave rectifier is

A.

1.21

B.

0.6

C.

0.482

D.

0.9

EXPLANATION

Option C is correct as seen in the table below:

Reference; https://cdn.instrumentationtools.com/wp-content/uploads/2016/07/instrumentationtools.com_half-wave-rectifiers-vs-full-wave-rectifiers.png

QUESTION:

Half wave voltage multiplier can provide any degree of voltage multiplication by cascading diodes and capacitors.

A.

any doubler

B.

any tripler

C.

any multiplication

D.

none of them

EXPLANATION

Option C is correct. Answer is in the question.

QUESTION:

A full wave rectifier passes _____ into positive cycles.

A.

Lower half cycle

B.

Upper half cycle

C.

Both cycles

D.

None of them

EXPLANATION

Both cycles are positive since the rectifier turns ac voltage into dc voltage.

QUESTION:

The maximum efficiency of full wave rectifier is ___.

A.

80.60%

B.

40.60%

C.

70%

D.

50%

EXPLANATION

It is a fact that maximum efficiency of a full wave rectifier is 80.60%.

QUESTION:

A circuit that adds positive or negative de voltage to an input sine wave is called ____.

A.

Clamper

B.

Clipper

C.

Diode clamp

D.

Limiter

EXPLANATION

A clamper is an electronic circuit that fixes either the positive or the negative peak excursions of a signal to a defined value by shifting its DC value.

QUESTION:

A half wave rectifier is operating from 50 Hz mains. The fundamental frequency of ripple will be ___.

A.

100 Hz

B.

25 Hz

C.

200 Hz

D.

50 Hz

EXPLANATION

As the output voltage obtained in a half wave rectifier circuit has a single variation in one cycle of ac voltage, hence the fundamental frequency in the ripple of output voltage would be = 50 Hz.

QUESTION:

The principle behind the working of cathode ray oscilloscope is?

A.

Oscillation

B.

Half-wave rectification

C.

Full wave rectification

D.

None of these

EXPLANATION

Option B is correct.

QUESTION:

Peak voltage in the output of half-wave rectifier is l0V so de component of the output voltage is?

A.

10 2

B.

10/ 2

C.

10/π

D.

10π

EXPLANATION

Through our knowledge, we know the peak voltage is fed with a sinusoidal signal without a filter which is 10V. Here we have a Half wave rectifier, so it nullifies one of the cycles of the input, and only one-half cycle is present in the output.

The output DC component of the half-wave rectifier is given by the formula,
Vdc = peak voltage (V0) / πVdc = 10/ π V.

QUESTION:

A full-wave rectifier is operating from 50Hz mains. The fundamental frequency of ripple will be?

A.

100 Hz

B.

25Hz

C.

50Hz

D.

200Hz

EXPLANATION

Full-wave rectification is a type of rectification in which output is obtained for both halves of a.c. Whereas, the frequency of the output is double that of the input. In a full-wave rectifier, the frequency of the ripple is double that of the main frequency. Hence ripple frequency = 100 Hz.

QUESTION:

The maximum efficiency of full wave rectifier is

A.

80.60%

B.

40.60%

C.

70%

D.

50%

EXPLANATION

A full wave rectifier converts AC signals into DC signals. The equation for a full wave rectifier is

given by

η=Pdc/Pac

Where Pdc is the DC power, while Pac is the input power. The max efficiency for a full wave rectifier is

81.2% ~ 80.6%.

QUESTION:

Average DC voltage across the load in terms of Vmax is:

A.

0.532

B.

0.637

C.

0.759

D.

0.437

EXPLANATION

The average DC voltage across the load is 0.637 Vmax.

Because the current flowing through the load is uni-directional, so the voltage developed across the load is also uni-directional, the same as for the previous two diode full-wave rectifier, therefore the average DC voltage across the load is 0.637 Vmax.

QUESTION:

In a half-wave rectification, during the negative cycle of the wave the diode is

A.

Reversed biased

B.

Forward biased

C.

Potential barrier

D.

None of these

EXPLANATION

Option A is correct since,during the negative cycle of the wave, the diode is reverse biased and does not allow that negative half to pass.

Option B is incorrect since a diode is forward biased during the positive half of the alternating cycle.

Option C is incorrect since the barrier potential is very high so applied voltage cannot exceed that, this is the reason for the reverse biasing of diodes.

Option D is incorrect since it states none of these, which is not the case.

QUESTION:

A half wave rectifier is equivalent to

A.

Clamper

B.

Clipper

C.

Clamper circuit with negative bias

D.

Clamper circuit with positive bias

EXPLANATION

Option B is correct since a clipper works to remove either the positive or negative half cycles of the input voltage. Since the diode most commonly allows the positive half cycles to pass through and not the negative, it acts as a positive clipper.

Option A is incorrect since clamping circuits place the negative and positive peaks of the waveform at the desired DC level. In other words, these circuits shift the input signal by an amount defined by the independent voltage source.

Option C is incorrect since a negative clamper circuit is biased with some negative reference voltage, that voltage will be added to the output to raise the clamped level.

Option D is incorrect since a positive clamper circuit is one that consists of a diode, a resistor, and a capacitor and that shifts the output signal to the positive portion of the input signal.

QUESTION:

The output voltage of a rectifier is:

A.

Smooth

B.

Pulsating

C.

Perfectly Direct

D.

Alternating

EXPLANATION

We can use the image below to come to the answer for this question.

QUESTION:

A full wave rectifier is operating from 50 Hz mains. Fundamental frequency of ripple will be

A.

100 Hz

B.

25 Hz

C.

50 Hz

D.

200 Hz

EXPLANATION

Option A is correct since the rate of flow of charge is current.

Option B is incorrect since the rate of flow of momentum is force.

Option C is incorrect since the rate of flow of power is not current.

Option D is incorrect since it states none of these, which is not the case.

QUESTION:

In a half wave rectification,during negative cycle of the wave the diode is?

A.

Reversed biased

B.

Forward biased

C.

Potential barrier

D.

None of these

EXPLANATION

In a half wave rectification, during the positive half cycle the diode is forward biased and during the negative half cycle the diode is reverse biased.

QUESTION:

Centre tape rectifier circuit consists of ______ diode.

A.

1

B.

200%

C.

300%

D.

400%

EXPLANATION

A Center tapped full wave rectifier has two diodes while a general full wave rectifier has 4 diodes.

QUESTION:

Peak voltage in the output of full wave rectifier is 10V so dc component of output voltage is:

A.

10√2

B.

20/√2

C.

20/π

D.

20π

EXPLANATION

As vdc = 2 vac / pi

vdc = 2(10) / pi

vdc = 20 / pi

QUESTION:

In which rectifier ripple factor is less?

A.

Full wave

B.

Half wave

C.

Both a) and b)

D.

None of them

EXPLANATION

In a full wave rectifier, lesser ripples are there in the output signal as compared to the half wave rectifier.

QUESTION:

A half wave rectifier is operating from 50 Hz mains. Fundamental frequency of ripple will be:

A.

100 Hz

B.

25 Hz

C.

200Hz

D.

50 Hz

EXPLANATION

In a half-wave rectifier, the ripple frequency of the output remains the same. So, if a half wave rectifier is operating from 50 Hz mains, the fundamental frequency of ripple will be the same i.e., 50Hz.

QUESTION:

Rectifier is a device which converts

A.

AC to DC

B.

DC to AC

C.

AC to triangular current

D.

DC to triangular current

EXPLANATION

Rectifier is an electronic device which is used to convert alternating current into direct current.

QUESTION:

Which of the following rectifier uses wheatstone bridge to rectify signal

A.

half wave

B.

full wave

C.

bridge

D.

All of the above

EXPLANATION

Full wave rectifiers use a wheatstone bridge arrangement to rectify the signal.

QUESTION:

In which rectifier ripple factor is less

A.

Full wave

B.

Half wave

C.

Both A&B

D.

None of them

EXPLANATION

In a full wave rectifier, the ripple factor is less than the half wave rectifier.

QUESTION:

For a half-wave rectifier having diode voltage VD and supply input of V, the diode conducts for π-2Θ, where Θ is given by

A.

tan-1(VD/V)

B.

sin-1(VD/V)

C.

cos-1(VD/V)

D.

cot-1(VD/V)

EXPLANATION

The diode doesn’t conducts when VD ≥VI . Hence Θ = sin-1(D/VI).

QUESTION:

The principle behind the working of cathode ray oscilloscope is which of the following?

A.

Oscillation

B.

Half wave rectification

C.

Full wave rectification

D.

None of these

EXPLANATION

Option B is correct since the basic principle behind the working of cathode ray oscilloscope is half wave rectification (fact).

QUESTION:

Average de Voltage across the load in terms of Vmax is which of the following?

A.

0.532 Vmax

B.

0.637Vmax

C.

0. 759Vmax

D.

0.437Vmax

EXPLANATION

Option B is correct since the current flowing through the load is unidirectional, so the voltage developed across the load is also unidirectional the same as for the previous two diode full-wave rectifiers, therefore the average DC voltage across the load is 0.637Vmax.

QUESTION:

Consider a peak rectifier fed by a 60-Hz sinusoid having a peak value Vp = 100 V. Let the load resistance R = 10 kn. Calculate the fraction of the cycle during which the diode is conducting.

A.

1.06 %

B.

2.06%

C.

3.18%

D.

4.28%

EXPLANATION

Option C is correct since the best explanation is :

w Δt ~ √(2Vr/Vp)

Θ = √(2 X 2/100)

Θ = 0.2 rad or 3.18% of the cycle

QUESTION:

Why is the bridge rectifier is preferred to an ordinary two diode full wave rectifier?

A.

it needs much smaller transformer for the same output

B.

No center tap required

C.

Less PIV rating per diode

D.

All of the above

EXPLANATION

Option D is correct since all the above-mentioned points are advantages of a bridge rectifier.

QUESTION:

In a centre tap full wave rectifier if Vm is the peak voltage across the secondary of transformer, the maximum voltage across reverse bias is ------

A.

Vm

B.

Vm/√2

C.

2Vm

D.

Vm/3

EXPLANATION

Option C is correct since:

QUESTION:

Half wave rectifier uses _____.

A.

One diode

B.

Two diodes

C.

Three diodes

D.

Four diodes

EXPLANATION

Half wave rectifier uses one diode to limit the flow of current in one direction only. This will allow only one half of the AC wave to pass through it.

QUESTION:

Half wave rectifier passes only _____.

A.

Lower half cycle

B.

Upper half cycle

C.

Both cycles

D.

None of them

EXPLANATION

The single-phase half-wave rectifier configuration above passes the positive half of the AC supply waveform with the negative half being eliminated.

QUESTION:

The bridge rectifier is preferred to an ordinary two diode full wave rectifier because _____.

A.

It needs much smaller transformer for the same output

B.

No center tap required

C.

Less PIV rating per diode

D.

All of the above

EXPLANATION

For a bridge rectifier, the Peak inverse voltage is less per diode and the rectifier uses a smaller transformer that does not require a tap. The ordinary two wave full rectifier, in comparison, produces the same output but with larger transformers and have higher PIV values per diode.

QUESTION:

In a rectifier, the larger the value of the shunt capacitor filter, _____.

A.

Larger the peak-to-peak value of the ripple voltage

B.

Larger the peak current in the rectifying diode

C.

Longer the time the current pulse flows through the diode

D.

Smaller the voltage across the load

EXPLANATION

C= ΔQ/ΔV = I x t/ΔV

If C increases, t increases for constant input power and voltage. Hence the time t for which current flows through the diode increases.

QUESTION:

If the line frequency is 50 Hz, the output frequency of bridge rectifier is ____.

A.

50Hz

B.

100Hz

C.

200Hz

D.

150Hz

EXPLANATION

Correct Option:B

This option is correct because in the output of bridge rectifiers one half cycle is repeated,the frequency will be twice as that of input frequency, so f=100Hz.

QUESTION:

Average DC voltage across the load in terms of Vmax is _____.

A.

0.532 Vmax

B.

0.637 Vmax

C.

0.759 Vmax

D.

0.437 Vmax

EXPLANATION

This option is correct because the current flowing through the load is unidirectional, so the voltage developed across is also unidirectional the same as for the previous two diode full-wave rectifiers, therefore the average DC voltage across the load is 0.67 Vmax.

QUESTION:

The use of a capacitor filter in a rectifier circuit gives satisfactory performance only when the load ____.

A.

Current is high

EXPLANATION

Correct Option: B (When the current is low a satisfactory performance is achieved)

QUESTION:

Which of the following is a type of rectifier?

A.

Half wave

B.

Full wave

C.

Bridge

D.

All of the above

EXPLANATION

Option D is correct.

Options A,B,C are incorrect because: These are all types of rectifiers.

QUESTION:

Ripple factor of half wave rectifier is ____.

A.

1.21

B.

0.8

C.

0.6

D.

0.4

EXPLANATION

Option A is correct because:

The ripple factor of the half wave rectifier is equal to 1.21 (i.e. γ = 1.21).

Options B,C,D are incorrect because: Wrong values.

QUESTION:

Half wave rectifier passes only ____.

A.

Lower half cycle

B.

Upper half cycle

C.

Both cycles

D.

None of them

EXPLANATION

Option B is correct because:

A half-wave rectifier removes the negative half cycle of an AC input and allows only the positive cycles to pass creating a DC flow.

Options A, C, and D are incorrect because the negative half cycle gets eliminated.

QUESTION:

A full wave rectifier is operating from 50 Hz mains. Fundamental frequency of ripple will be ____.

A.

100 Hz

B.

25 Hz

C.

50 Hz

D.

200 Hz

EXPLANATION

Option A is correct because:

In a full wave rectifier, we get the output for the positive and negative cycle of input a.c. Hence the frequency of the ripple of the output is twice than that of input a.c. i.e. 100Hz

Options B,C,D are incorrect because: Wrong values

QUESTION:

Which of the following is not a type of rectifier?

A.

Phase wave rectifier

B.

Full wave

C.

Half wave

D.

None of these options are correct

EXPLANATION

Option A is correct since a phase wave rectifier is a device that rectifies the input AC voltage.

Options B and C are incorrect since half and full waves are the types of a rectifier.

Option D is incorrect since option A is the right answer.

QUESTION:

A full wave rectifier is operating from 50 Hz mains. Fundamental frequency of ripple will be ______.

A.

100 Hz

B.

25 Hz

C.

50 Hz

D.

200 Hz

EXPLANATION

Option A is correct since in a full wave rectifier the frequency of ripple will be double to that of main frequency, so 100Hz.

Options B, C, and D are incorrect since they are wrong answers.

QUESTION:

Rectifier is a device which converts _____.

A.

AC to DC

EXPLANATION

Rectifier is a device that is used to convert Alternating Current to a Direct Current. Hence Option A is correct.

QUESTION:

In a full-wave rectifier with input frequency 50Hz, the ripple in the output is mainly of frequency _____.

A.

25Hz

B.

50Hz

C.

100Hz

D.

Zero

EXPLANATION

The frequency of the output voltage or current in a full-wave rectifier is double the input frequency. Therefore an input of 50 Hz will generate an output of 100 Hz. Hence Option C is correct.

QUESTION:

The ripple factor of a full-wave rectifier is ____.

A.

1.21

B.

0.5

C.

0.482

D.

0.9

EXPLANATION

This is a value to memorized. The ripple factor of a full-wave rectifier is 0.482. Hence Option C is correct.

QUESTION:

The output voltage of a rectifier is ______.

A.

Smooth

B.

Pulsating

C.

Perfectly direct

D.

Alternating

EXPLANATION

A rectifier always converts an Alternating Voltage/Current to a pulsating Direct Voltage/Current. Hence Option B is correct.

QUESTION:

In a center tap full-wave rectifier, if Vm is the peak voltage across the secondary coil of the transformer, the maximum voltage across reverse bias is _____.

A.

Vm

B.

Vm/√2

C.

2Vm

D.

Vm/√3

EXPLANATION

Peak inverse voltage or peak reverse voltage is the maximum voltage a diode can withstand in the reverse bias condition. This voltage will be double the peak voltage. So 2Vm. Hence Option C is correct.

QUESTION:

In a half wave rectification, during negative cycle of the wave the diode is ______.

A.

Reversed biased

EXPLANATION

During half-wave rectification of AC, during one half of the cycle, the diode is forward biased while during the other half (negative cycle), it is reversed biased. Hence, Option A is correct.

QUESTION:

If a half wave rectifier is used to convert 50Hz AC into DC, then the number of pulses present in rectifier voltage is _____.

A.

25

B.

50

C.

100

D.

75

EXPLANATION

If, for example, a 2 Hz (2 cycles per second) input alternating voltage is half-wave rectified, the output signal will have two peaks, one from each cycle, in one second. So if a 50 Hz alternating voltage is half-wave rectified, the output will have 50 pulses/peaks. Hence, Option B is correct.

QUESTION:

The number of diodes in bridge rectifier is _____.

A.

4

B.

3

C.

2

D.

5

EXPLANATION

A full-wave bridge rectifier circuit uses four diodes. Hence, Option A is correct.

QUESTION:

Input resistance of an Operational Amplifier is:

A.

Very low

B.

Very high

C.

Moderate

D.

Becomes infinite

EXPLANATION

The input resistance is infinite for an ideal OP-AMP which prevents current from flowing into the OP-AMP itself as it may damage the component. However, since we are not talking about an ideal situation, in real life the resistance is not infinite rather very high thus the answer is B.

QUESTION:

Operational amplifier with an LDR is used as a:

A.

Half wave rectifier

B.

Gate

C.

Night switch

D.

Full wave rectifier

EXPLANATION

C is the answer as the polarity of the output of the OP-AMP would change based on the input and since the LDR is placed on one of the inputs, we can say that the output polarity is dependent on the light intensity which is perfect for a night switch.

QUESTION:

A capacitor and an inductor are connected to A.C. supply. If we double the frequency of A.C. supply then the effect on reactance of capacitor XC and reactance of inductor XL will be:

A.

Both XC and XL are doubled

B.

Both XC and XL are halved

C.

XC is doubled and XL reduces to half

D.

XL is doubled and XC reduces to half

E.

Both XC and XL are unchanged

EXPLANATION

The inductive reactance of an inductor increases as the frequency across it increases therefore inductive reactance is proportional to frequency ( XL α ƒ )

The capacitive reactance of the capacitor decreases as the frequency across it increases therefore capacitive reactance is inversely proportional to frequency.

QUESTION:

When an Operational amplifier is used as Inverting amplifier, then angle between its output and input signal is:

A.

30 degrees

B.

45 degrees

C.

60 degrees

D.

90 degrees

E.

180 degrees

EXPLANATION

It is called Inverting Amplifier because the op-amp changes the phase angle of the output signal exactly 180 degrees out of phase with respect to input signal.

QUESTION:

A capacitor and an inductor are connected to A.C. supply. If we double the frequency of A.C. supply then the effect on reactance of capacitor XC and reactance of inductor XL will be:

A.

Both XC and XL are doubled

B.

Both XC and XL are halved

C.

XC is doubled and XL reduces to half

D.

XL is doubled and XC reduces to half

E.

Both XC and XL are unchanged

EXPLANATION

The inductive reactance of an inductor increases as the frequency across it increases therefore inductive reactance is proportional to frequency ( XL α ƒ )

The capacitive reactance of the capacitor decreases as the frequency across it increases therefore capacitive reactance is inversely proportional to frequency.

QUESTION:

When an Operational amplifier is used as Inverting amplifier, then angle between its output and input signal is:

A.

30 degrees

B.

45 degrees

C.

60 degrees

D.

90 degrees

E.

180 degrees

EXPLANATION

It is called Inverting Amplifier because the op-amp changes the phase angle of the output signal exactly 180 degrees out of phase with respect to input signal.

QUESTION:

When reverse bias of a p-n junction diode is increased, a stage comes when electric field set up is sufficient to rupture covalent bonds and release a large number of holes and electrons. This breakdown phenomenon is known as:

A.

Avalanche breakdown

B.

Zoner breakdown

C.

Early effect

D.

High - field emission

EXPLANATION

Avalanche breakdown (or “the avalanche effect”) is a phenomenon that can occur in both insulating and semiconducting materials. It is a form of electric current multiplication that can allow very large currents within materials which are otherwise good insulators. It is a type of electron avalanche.

QUESTION:

If both inputs “A” and “B” are ON and the output is also ON. This type of gate is known as:

A.

OR Gate

B.

AND Gate

C.

NAND Gate

D.

NOR Gate

EXPLANATION

Technically, the answer can either be A or B here because putting ON at both inputs will give ON in both, as an output. But we will choose B here, since this condition is specific here. Only ON and ON give ON in AND, while OR gate can give ON with other combinations too.

QUESTION:

______ is equivalent to AND Gate followed by a NOT Gate.

A.

NOR Gate

B.

NAND Gate

C.

NOT Gate

D.

None of these

EXPLANATION

When the AND and NOT gate are combined it forms a NAND gate. Outputs are opposite to the AND gate.

QUESTION:

Which option in the following best explains Base of a transistor?

A.

Base has no impurity

B.

Base has less concentration of impurity as compared to emitter and collector

C.

Base has more concentration of impurity as compared to emitter

D.

Base has more concentration of impurity as compared to collector

EXPLANATION

This is also the reason that base is very lightly doped because its only purpose is to act as a control for the collector current

QUESTION:

A logic gate has four inputs. Its possible input combinations will be:

A.

4

B.

16

C.

32

D.

64

EXPLANATION

This can be calculated using the formula 2n, where n is the number of possible inputs.

The number of inputs is 4. the each input will take 0 OR 1 as values Therefore 24 = 16 possible combinations of inputs are there as

QUESTION:

In a npn transistor, the current IE that flows in the emitter circuit is:

A.

IC + IB

B.

IC - IB

C.

IC x IB

D.

Zero

EXPLANATION

Emitting current=Collecting current+Base current.

QUESTION:

In photodiodes, the bias voltage is applied in ______ bias form.

A.

Forward

B.

Resistance

C.

Reverse

D.

Converse

EXPLANATION

The photodiode is reverse biased for operating in the photoconductive mode. As the photodiode is in reverse bias the width of the depletion layer increases. This reduces the junction capacitance and thereby the response time. In effect, the reverse bias causes faster response times for the photodiode.

QUESTION:

A semiconductor photodiode is a:

A.

reverse biased junction diode

B.

forward biased junction diode

C.

half wave rectifier

D.

full wave rectifier

E.

Transistor

EXPLANATION

The photodiode is reverse biased for operating in the photoconductive mode. As the photodiode is in reverse bias the width of the depletion layer increases. This reduces the junction capacitance and thereby the response time. In effect, the reverse bias causes faster response times for the photodiode.

QUESTION:

A negligible small current between input terminals of the operational amplifier is because of:

A.

High output resistance

B.

Low output resistance

C.

High input resistance

D.

Low input resistance

EXPLANATION

Ideal op-amps have zero input current. A small input current passes because of very high input impedence.

QUESTION:

A signal of -80 mV is applied to the inverting terminal of the amplifier while the non inverting terminal is grounded. The gain of the amplifier is 25 using Rin(R1) equal to 3 ohms and Rf(R2) equal to 75 Ohms. What would be the value of the output signal?

A.

200 mV

B.

-3 V

C.

2 V

D.

3 V

EXPLANATION

Since Gain = 25

Vout = Vin * Gain = -80mv * 25 = -2000 mv = -2V = 2V**

** since a positive-going voltage at the inverting terminal gives a negative-going output voltage, hence the answer is positive 2V.

QUESTION:

When we apply input at the non-inverting input of an operational amplifier then the output appears after:

A.

Amplification, phase shift of 180˚

B.

Amplification, phase shift of 60˚

C.

Amplification, no phase shift

D.

None of the given options

EXPLANATION

The voltage gain is always greater than one. The voltage gain is positive, indicating that for AC input, the output is in-phase with the input signal and amplified

QUESTION:

Which of the following is false?

A.

In P-type substance majority charge carriers are holes

B.

During forward biasing of a divide width of depletion region decreases

C.

Leakage current flows to minority charge carriers

D.

None of the given options

EXPLANATION

All the options are true

QUESTION:

Which of the following is not true about LEDs?

A.

There are two wires (called leads) attached to an LED

B.

While connecting to a circuit, the longer lead of LED is always connected to the positive terminal of the battery

C.

While connecting to a circuit, the shorter lead of LED is always connected to the positive terminal of the battery

D.

LED can be used to detect weak current

EXPLANATION

While connecting to a circuit, the longer lead is always connected to the positive terminal of the battery and the shorter lead is connected to the negative terminal of the battery.

QUESTION:

Which of the following is the truth table for the logic gate:

A.

A

B.

B

C.

C

D.

D

EXPLANATION

Explanation will be added soon

QUESTION:

If the fundamental logic gates are connected as:

A.

A

B.

B

C.

C

D.

D

EXPLANATION

Explanation will be added soon

QUESTION:

Three NAND gates are connected as shown in the figure.
Which of the following logic gates is formed in the connected circuit?

A.

OR

B.

AND

C.

NOR

D.

NAND

EXPLANATION

We can check to which gate this diagram refers to by sending in 1 from A and 0 from B.
Output at X, after working, will be 1. This means that this gate is working as an OR gate. As
only in OR gate, when two inputs are 1 and 0 respectively the output is 1.

QUESTION:

What is the output of the truth table?

A.

B.

A AND C

C.

B

D.

NO CORRECT OPTION

EXPLANATION

A.B means that AAND B imply that 0 AND 0 should give 0,1 and 0 should give 0 and 1 and
1 should give 1.
This makes the equation for four Xs as
0 OR 0=0
0 OR 0=0
0 OR 0=0
1 OR 1=1

QUESTION:

The difference between the plates of a parallel plate capacitor is 2.0 mm and area of
each plate is 2.0 m^2. The plates are in a vacuum. A potential difference of 1.0 x
10^4 V is applied across the plates. Find the capacitance.

A.

4 x 10-3 F

B.

3.54 x 10-9 F

C.

8.85 x 10-9 F

D.

9.0 x 10-9 F

EXPLANATION

The capacitance of a parallel plate capacitor is C=ϵ0Ad
C=(8.85x10^-12)*(2)*(2x10^-3)=3.54 x 10^-9C

QUESTION:

Which of the following techniques is the practical application of X-rays?

A.

Magnetic Resonance Imaging

B.

Ultrasonography

C.

Computerized Axial Topography

D.

Positron Emission Tomography

EXPLANATION

Computed tomography (CT) scanning, also known as, especially in the older
literature and textbooks, computerized axial tomography (CAT) scanning, is a
diagnostic imaging procedure that uses x-rays to build cross-sectional images
(slices) of the body.

QUESTION:

Which one of the following spectra is most typical of the output of an X-ray tube?

A.

A

B.

B

C.

C

D.

D

EXPLANATION

The most typical outcome of an X-ray tube is shown in B, which is a factual recall from the
book

QUESTION:

Which one of the following has the largest energy content?

A.

γ-rays

B.

X-rays

C.

Infra-red radiations

D.

Ultra-violet radiations

EXPLANATION

Gamma rays have the highest energy in all of the above mentioned, it is because of their
highest frequency among all, as shown below:

QUESTION:

What will be the energy of the accelerated electron used to produce X-rays when the
accelerating potential is 2 kV?

A.

2 x 10-19 J

B.

1.6 x 10-19 J

C.

3.2 x 1019 J

D.

3.2 x 10-16 J

EXPLANATION

The formula relating energy, charges, and voltages is:ΔPE = qΔV.
PE=(2x10^3)*(1.6x10^-19)
PE=3.2x10^-16 J.

QUESTION:

Process of generating three dimensional images of objects by using laser beam is called

A.

Photography

B.

3-D cinema

C.

Holography

D.

Tomography

EXPLANATION

Holography is a process that creates three-dimensional images called holograms
using laser beams, the properties of interference and diffraction, light intensity
recording, and illumination of the recording.

QUESTION:

What is the output Boolean expression of logic diagram shown in figure below:

A.

A

B.

B

C.

C

D.

D

EXPLANATION

The outputs of each NAND gate is given by AB and AB, making them the 2 inputs for the OR gate, so the final output X would be AB+AB.

QUESTION:

Which of the following is the proper way to study the sinusoidal wave form of voltage?

A.

Voltage is connected to ‘Y’ input and time base is switched on

B.

Voltage is connected to ‘X’ input and time base is switched off

C.

Voltage is connected to ‘Y’ input and time base is switched off

D.

Voltage is connected to ‘X’ input and time base is switched on

EXPLANATION

Voltage should be connected to Y and timebase switched on.

QUESTION:

What is the logic symbol for a NOT Gate?

A.

Option A

B.

Option B

C.

Option C

D.

Option D

EXPLANATION

In the following diagrams, A is a NOT gate. B is a OR gate, C is AND gate and D is a symbol for PN junction diode.

QUESTION:

Which one of the following is I-V curve of a junction diode?

A.

Option A

B.

Option B

C.

Option C

D.

Option D

EXPLANATION

The primary function of a semiconductor diode is rectification of AC to DC. When a diode is forward biased ; the higher potential is connected to its Anode, it will pass current. When the diode is reverse biased ; the higher potential is connected to its Cathode, the current is blocked.
Then a PN junction needs a bias voltage of a certain polarity and amplitude for current to flow. This bias voltage also controls the resistance of the junction and therefore the flow of current through it.
This can further be explained by the diagram below

QUESTION:

Which of the following rectifier uses wheatstone bridge to rectify signal:

A.

Half wave

B.

Full wave

C.

Bridge

D.

Both half and full wave

EXPLANATION

Bridge rectifier is formed by connecting four diodes in the form of a Wheatstone bridge. It also provides full wave rectification.

QUESTION:

A full wave rectifier passes _________ into positive cycles:

A.

Lower half cycle

B.

Upper half cycle

C.

Both lower and upper half cycles

D.

One quarter cycle

EXPLANATION

Refer to the following diagram of full wave rectification.

QUESTION:

In the case of germanium, the value of potential barrier develops across the depletion region is

A.

0v

B.

0.3V

C.

0.7V

D.

0.9V

EXPLANATION

Typically at room temperature the voltage across the depletion layer for germanium is about 0.3 – 0.35 volts.

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