Most Important Electronics Quiz Test Online

Electronics Quiz Test Online

Electronics Test. 1

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1) When a transistor is used as a digital switch, it operates in which two regions?

Cut-off and Active

Saturation and Cut-off

Active and Saturation

Active and Breakdown

As a switch, a transistor is either fully OFF (Cut-off region) or fully ON (Saturation region), representing the two states of a digital signal.

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2) In a PNP transistor, the charge carriers are mainly:

Ions

Electrons

Both electrons and holes

Holes

In a PNP transistor, the emitter and collector are p-type materials, so holes are the majority charge carriers.

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3) The process of adding impurities to a pure semiconductor is called:

Doping

Diffusion

Depletion

Annealing

This is the correct term for intentionally introducing impurities into a semiconductor to alter its electrical properties.

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4) The relationship between alpha and beta is:

alpha = beta / (1 - beta)

alpha = beta / (1 + beta)

beta = alpha / (1 - alpha)

beta = alpha / (1 + alpha)

This is the correct relationship derived from the basic transistor current equations.

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5) In a common-emitter transistor, the emitter current (Ie) is 8.0 mA and the collector current (Ic) is 7.9 mA. What is the current gain (beta)?

0.98

First, find the base current: Ib = Ie - Ic = 8.0 - 7.9 = 0.1 mA. Then, calculate beta: β = Ic / Ib = 7.9 mA / 0.1 mA = 79.

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6) When a p-n junction is forward biased, the width of the depletion region:

Increases

Decreases

Remains the same

Becomes zero

The applied forward voltage opposes the built-in potential, reducing the width of the depletion region and allowing current to flow.

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7) A transistor has how many doped regions?

A transistor consists of three doped regions: the emitter, base, and collector.

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8) In a semiconductor, the forbidden energy gap is of the order of:

1 MeV

10 eV

0.1 eV

1 eV

This value is characteristic of the energy required to move an electron from the valence band to the conduction band in a semiconductor.

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9) What is the primary function of a capacitor placed in parallel with the load resistor in a rectifier circuit?

To increase the frequency of the output voltage

To block the DC component

To protect the diode from excessive reverse voltage

To store charge during peaks and supply it to the load during troughs

The capacitor acts as a filter. It charges up to the peak voltage of the rectifier's output and then discharges slowly through the load when the output drops, thus smoothing the DC signal.

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10) The base of a transistor is:

Heavily doped and thick

Lightly doped and thin

Heavily doped

Moderately doped and thick

This design allows most of the charge carriers from the emitter to pass through to the collector.

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11) A Zener diode is designed to operate in the:

Cut-off region

Saturation region

Reverse breakdown region

Forward bias region

This is the region where the Zener diode maintains a constant voltage, making it useful for voltage regulation.

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12) In a half-wave rectifier, the output frequency is _______ the input frequency.

Equal to

Double

Half

Zero

A half-wave rectifier produces one output pulse for each input cycle, so the frequency remains the same.

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13) The current gain of a common-emitter amplifier is given by the symbol:

beta

alpha

delta

gamma

Beta is the symbol for the current gain in a common-emitter configuration, defined as the ratio of collector current to base current.

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14) The V-I characteristic curve for a silicon diode is shown. The point 'V_k' on the graph represents the:

Knee Voltage

Breakdown Voltage

Peak Inverse Voltage

Zener Voltage

The point 'V_k' where the current starts to increase rapidly in forward bias is called the knee voltage or cut-in voltage, which is approximately 0.7 V for silicon.

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15) A diode is a device that allows current to flow in:

A circular path

Both directions

Neither direction

One direction only

This is the defining characteristic of a diode, which acts as a one-way gate for current.

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16) For a transistor to act as an amplifier, the emitter-base junction must be:

Both junctions reverse biased

Both junctions forward biased

Reverse biased and the collector-base junction forward biased

Forward biased and the collector-base junction reverse biased

This is the standard biasing condition for a transistor to operate in the active region and function as an amplifier.

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17) A photodiode is operated in:

Reverse bias

No bias

Breakdown region

Forward bias

In reverse bias, the small reverse current is proportional to the intensity of light falling on the photodiode.

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18) The process of converting AC to DC is called:

Modulation

Oscillation

Rectification

Amplification

This is the correct term for converting alternating current (AC) into direct current (DC).

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19) The depletion region of a p-n junction is so named because it is depleted of:

Mobile charge carriers

Atoms

Potential barrier

Impurities

This region is formed by the diffusion of electrons and holes across the junction, leaving behind immobile ions.

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20) In a p-type semiconductor, the majority charge carriers are:

Neutrons

Protons

Electrons

Holes

P-type semiconductors are created by doping with trivalent impurities, which creates an excess of holes.

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Electronics Test. 2

1 / 20

1) The voltage gain of a non-inverting op-amp is given by:

Av = Rf/Ri

Av = 1 + Rf/Ri

Av = 1 - Rf/Ri

Av = -Rf/Ri

This is the correct formula for the voltage gain of a non-inverting op-amp, which is always greater than or equal to 1.

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2) The ripple factor of a full-wave rectifier is:

0.48

1.21

1.0

0.81

This is the approximate ripple factor for a full-wave rectifier, which is much lower than that of a half-wave rectifier.

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3) The binary number system has a base of:

The binary system uses only two digits, 0 and 1, hence its base is 2.

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4) Which of the following is a digital quantity?

Speed of a car

Height of a person

Temperature of a room

Number of students in a class

This is a discrete, whole number, which is a digital quantity.

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5) An operational amplifier (op-amp) has a very high:

Current gain

Input impedance

Power consumption

Output impedance

A high input impedance is a key characteristic of an op-amp, allowing it to draw very little current from the input source.

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6) Which logic gate is known as the universal gate?

XOR

AND

NAND

The NAND gate is a universal gate because any other logic function can be created using only NAND gates.

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7) A NOT gate is also known as an:

Follower

Inverter

Buffer

Converter

The NOT gate inverts the input signal, so it is also called an inverter.

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8) An ideal operational amplifier (Op-Amp) should have:

High input impedance and high output impedance

High input impedance and very low output impedance

Low input impedance and low output impedance

Low input impedance and high output impedance

An ideal op-amp has infinite input impedance (so it draws no current from the source) and zero output impedance (so it can deliver maximum voltage to the load).

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9) In an inverting amplifier, the output signal is:

90 degrees out of phase with the input signal

180 degrees out of phase with the input signal

In phase with the input signal

Independent of the input signal

The inverting configuration of an op-amp produces an output that is a magnified and inverted version of the input.

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10) The Boolean expression for an OR gate is:

Y = (A + B)'

Y = A'

Y = A + B

Y = A . B

This represents the OR operation in Boolean algebra.

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11) The decimal equivalent of the binary number 1011 is:

The calculation is (1 x 2^3) + (0 x 2^2) + (1 x 2^1) + (1 x 2^0) = 8 + 0 + 2 + 1 = 11.

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12) The conductivity of an intrinsic semiconductor increases with an increase in temperature primarily because:

The forbidden energy gap increases

The number of charge carriers (electron-hole pairs) increases

The semiconductor becomes a p-type material

The mobility of charge carriers increases

Higher temperatures provide thermal energy to break covalent bonds, creating more free electrons and holes, which increases the density of charge carriers and thus conductivity.

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13) The output of a NOR gate is HIGH only when:

Any input is LOW

Any input is HIGH

All inputs are HIGH

All inputs are LOW

This is the only condition under which the output of a NOR gate is HIGH.

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14) A bistable multivibrator is also known as a:

Flip-flop

Counter

Clock

A flip-flop is a bistable multivibrator, meaning it has two stable states and can store one bit of information.

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15) In a common-emitter amplifier, the output voltage is taken from the:

Emitter

Collector

Ground

Base

The output is taken from the collector terminal.

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16) In a common-base amplifier, the current gain alpha is always:

Greater than 1

Infinite

Less than 1

Equal to 1

Alpha is the ratio of collector current to emitter current, and since some current is lost in the base, the collector current is always slightly less than the emitter current.

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17) The efficiency of a full-wave rectifier is approximately:

100%

81.2%

40.6%

50%

A full-wave rectifier is twice as efficient as a half-wave rectifier.

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18) An oscillator is a circuit that produces:

An amplified output from a small input

A constant voltage output

A periodic waveform without any input signal

A DC output from an AC input

An oscillator is a self-sustaining circuit that generates a repetitive output signal.

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19) An LED (Light Emitting Diode) emits light when:

It is heated

Forward biased

Reverse biased

No bias is applied

When forward biased, electrons and holes recombine at the junction, releasing energy in the form of photons (light).

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20) The output of an AND gate is HIGH only when:

All inputs are LOW

Any input is HIGH

All inputs are HIGH

Any input is LOW

This is the defining characteristic of the AND gate.

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Electronics Test. 3

1 / 20

1) De Morgan's first theorem states that (AB)' is equal to:

A'B'

A' + B'

A + B

A' + B

This is the correct statement of De Morgan's first theorem, which relates the NAND and OR operations.

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2) The resistance of a reverse-biased p-n junction is:

Very high

Infinite

Zero

Very low

The wide depletion region in a reverse-biased junction offers a very high resistance to current flow.

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3) The Boolean expression A + A'B is equivalent to:

A + B

This is the correct simplification using the rules of Boolean algebra: A + A'B = (A + A')(A + B) = 1(A + B) = A + B.

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4) The collector of a transistor is:

Not doped

Heavily doped

Moderately doped and largest in size

Lightly doped

The collector is moderately doped to reduce its resistance and is the largest region to dissipate heat.

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5) A device that converts electrical energy into light energy is:

LED

Photodiode

Zener diode

Rectifier diode

An LED (Light Emitting Diode) is specifically designed for this energy conversion.

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6) Zener breakdown in a p-n junction occurs due to:

The collision of minority carriers with atoms

The diffusion of majority carriers across the junction

The rupture of covalent bonds by a strong electric field

The thermal breakdown of covalent bonds

Zener breakdown happens in heavily doped diodes with a narrow depletion region, where the intense electric field is strong enough to directly break covalent bonds and create carriers.

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7) A transistor can be used as a:

Neither a switch nor an amplifier

Switch

Both a switch and an amplifier

Amplifier

Depending on its biasing, a transistor can function as either a switch or an amplifier.

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8) The potential barrier for silicon at room temperature is approximately:

1.5 V

0.3 V

1.1 V

0.7 V

This is the typical value for the potential barrier of a silicon p-n junction.

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9) An op-amp can be used as a comparator to:

Store a voltage

Compare two voltages

Generate a sine wave

Amplify a single voltage

In its open-loop configuration, an op-amp's output saturates to one of its supply voltages depending on which input has a higher potential.

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10) The output of an XOR gate is HIGH when:

The inputs are different

The inputs are the same

Both inputs are HIGH

Both inputs are LOW

The XOR (Exclusive OR) gate gives a HIGH output only when the inputs are different.

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11) What is the result of the binary addition 1101 + 0110?

10111

10011

10001

11111

Starting from the right: 1+0=1. 0+1=1. 1+1=0 with a carry of 1. 1+0+1(carry)=0 with a carry of 1. The final result is 10011.

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12) A filter circuit is used to:

Smooth the pulsating DC output of a rectifier

Regulate the DC output

Convert AC to DC

Amplify the DC output

A filter, typically a capacitor, is used to remove the AC components (ripples) from the rectifier's output.

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13) The number of diodes required in a center-tapped full-wave rectifier is:

This type of rectifier uses two diodes, one for each half of the AC cycle.

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14) The phase difference between the input and output of a common-emitter amplifier is:

180 degrees

270 degrees

0 degrees

90 degrees

The common-emitter configuration inverts the input signal, resulting in a 180-degree phase shift.

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15) In a bridge rectifier, how many diodes are used?

A bridge rectifier uses four diodes arranged in a bridge configuration to achieve full-wave rectification without a center-tapped transformer.

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16) A logic circuit consists of a two-input AND gate followed by a NOT gate. This combination is equivalent to a single:

OR gate

XOR gate

NAND gate

NOR gate

The function of an AND gate is Y = A.B. Inverting this output with a NOT gate gives Y = (A.B)', which is the definition of a NAND gate.

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17) Which of the following is an active component?

Transistor

Capacitor

Inductor

Resistor

A transistor is an active component because it can amplify a signal, which requires an external power source.

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18) In a conductor, the valence band and conduction band:

Are separated by a large gap

Overlap each other

Are both empty

Are separated by a small gap

The overlapping of these bands allows electrons to move freely, resulting in high conductivity.

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19) The gain of an amplifier without feedback is known as:

Open-loop gain

Voltage gain

Closed-loop gain

Current gain

This is the term for the intrinsic gain of the amplifier itself, without any feedback circuit.

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20) In the circuit shown, if the input is a sine wave, which component is primarily responsible for converting the pulsating DC into a smoother DC?

Capacitor C

Transformer

Diode D1

Load Resistor R_L

The diode (D1) performs rectification (AC to pulsating DC). The capacitor (C) acts as a filter, smoothing the pulsating DC by storing and releasing charge, thereby reducing the ripple.

Your score is

The average score is 90%

Most Important Electronics Quiz Test Online

Electronics Quiz Test Online

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Electronics Quiz Test Online

Other Physics Topics Quiz

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