1.
The forward voltage drop of a conducting silicon diode is approximately:
Correct Answer
B. 0.6 V
Explanation
The forward voltage drop of a conducting silicon diode is approximately 0.6 V. This is because silicon diodes have a forward voltage drop of around 0.6 to 0.7 V when they are conducting current. This voltage drop is due to the energy required to overcome the barrier potential at the junction between the P-type and N-type materials in the diode.
2.
The frequency of the ripple voltage present on the output of a bridge of a bridge rectifier fed from a 400 Hz Ac supply will be:
Correct Answer
A. 200 Hz
Explanation
The frequency of the ripple voltage on the output of a bridge rectifier is twice the frequency of the input AC supply. In this case, the input AC supply is 400 Hz, so the frequency of the ripple voltage will be 2 times 400 Hz, which is 800 Hz.
3.
Which one of the following relationships is correct for a BJT:
Correct Answer
B. Collector current = emitter current - base current
Explanation
The correct relationship for a BJT is that the collector current is equal to the sum of the emitter current and the base current. This is because in a BJT, the collector current is formed by the combination of the emitter current and the base current. The base current controls the amount of current flowing from the emitter to the collector, so the collector current is equal to the sum of these two currents.
4.
A transistor operates with a base current of 45 mA and a collector current of 1.8 A. Which of the following gives the current gain of the device when used in common-emitter configuration?
Correct Answer
A. 40
Explanation
The current gain of a transistor in common-emitter configuration is given by the ratio of the collector current to the base current. In this case, the collector current is 1.8 A and the base current is 45 mA. Dividing the collector current by the base current gives a current gain of 40.
5.
A typical application for a zener diode is:
Correct Answer
A. Voltage stabilization
Explanation
A zener diode is specifically designed to operate in the reverse breakdown region, which allows it to maintain a constant voltage across its terminals when the current flowing through it exceeds a certain threshold. This makes it ideal for voltage stabilization applications, where a steady voltage is required regardless of variations in input voltage or load conditions. Power rectification involves converting alternating current (AC) to direct current (DC), which is not the primary purpose of a zener diode. Signal detection typically involves using diodes in a different configuration, such as a signal diode or a Schottky diode, rather than a zener diode.
6.
A practical operational amplifier has:
Correct Answer
A. Very high input impedance and very high voltage gain
Explanation
A practical operational amplifier has a very high input impedance, which means that it draws very little current from the input signal source. This allows the input signal source to deliver its full voltage without being affected by the amplifier's input impedance. Additionally, a practical operational amplifier has a very high voltage gain, which means that it amplifies the input voltage signal by a large factor. This allows the amplifier to provide a much larger output voltage than the input voltage.
7.
A thyristor has which of the following:
Correct Answer
B. High resistance when switched off
Explanation
When a thyristor is switched off, it exhibits high resistance. This is because, in the off state, the thyristor blocks the flow of current and acts like an open circuit. As a result, the resistance offered by the thyristor is high. However, when the thyristor is switched on, it offers a low resistance path for current flow. Hence, the given answer correctly states that a thyristor has high resistance when switched off.
8.
The anode of a silicon diode is connected to a +5V DC supply and the cathode is connected to a +4V DC supply. The diode is:
Correct Answer
C. Forward biased and conducting
Explanation
In the scenario described, the anode of the silicon diode is connected to a higher positive voltage (+5V DC) than the cathode, which is connected to a lower positive voltage (+4V DC). This configuration is known as forward bias. In a forward-biased state, the diode allows current to flow through it, and it conducts. Therefore, in this case, the diode is forward biased and conducting.
9.
The connections on a thyristor (silicon-controlled rectifier) are labelled:
Correct Answer
A. Anode, cathode, gate
Explanation
The connections on a thyristor are labelled as anode, cathode, and gate. The anode is the positive terminal, the cathode is the negative terminal, and the gate is used to control the flow of current between the anode and cathode.
10.
In the bridge rectifier arrangement shown, the DC output is taken from:
Correct Answer
A. A and C
Explanation
The DC output is taken from points A and C in the bridge rectifier arrangement because these two points are connected to the positive and negative terminals of the load respectively. The bridge rectifier circuit converts the alternating current (AC) input into direct current (DC) output by using a combination of diodes. The diodes in the circuit ensure that the current flows in one direction only, allowing the DC output to be taken from points A and C.
11.
The device shown is used for:
Correct Answer
A. Power control
Explanation
The device shown is used for power control. This can be inferred because power control involves regulating the amount of power being supplied or consumed by a device or system, and the device shown appears to have buttons or switches that can be used to adjust or control the power.
12.
When a transistor is used in common-emitter mode:
Correct Answer
A. The input is taken to the base and and output is taken from the collector
Explanation
In common-emitter mode, the input signal is applied to the base terminal of the transistor, while the output signal is taken from the collector terminal. This configuration allows for amplification of the input signal, as the base current controls the collector current, resulting in a larger output signal at the collector.
13.
The typical common-emitter current gain for a bipolar transistor is:
Correct Answer
C. More than 40
Explanation
The correct answer is "more than 40". This means that the typical common-emitter current gain for a bipolar transistor is greater than 40. In other words, when the transistor is in the common-emitter configuration, the output current is amplified by a factor of more than 40 compared to the input current. This indicates that the transistor has a high current amplification capability in this configuration.
14.
The device shown is:
Correct Answer
C. An NPN transistor
Explanation
The device shown is an NPN transistor. This can be determined by the orientation of the arrow in the symbol, which indicates that it is an NPN transistor. In an NPN transistor, the base terminal is made of P-type material, while the emitter and collector terminals are made of N-type material. The flow of current in an NPN transistor is from the emitter to the collector, with the base controlling the current flow.
15.
The region in a P-N junction diode where no free charge carriers exists is known as the:
Correct Answer
B. Depletion region
Explanation
The region in a P-N junction diode where no free charge carriers exist is known as the depletion region. In this region, the P-N junction creates an electric field that causes the majority charge carriers (electrons in the N-region and holes in the P-region) to move away from the junction, leaving behind immobile ions. This depletion of charge carriers creates a region depleted of free charge carriers, hence the name "depletion region".
16.
The forward voltage drop of a conducting silicon diode is approximately:
Correct Answer
B. 0.6 V
Explanation
A conducting silicon diode typically has a forward voltage drop of approximately 0.6 V. This means that when a forward bias voltage is applied to the diode, it requires a minimum of 0.6 V to start conducting current. This voltage drop is due to the energy barrier between the p-type and n-type regions of the diode, which must be overcome for current to flow.
17.
A logic 1 is present at the output of a two-input NOR gate. Which one of the following is true?
Correct Answer
B. Both of its input must be at logic 0
Explanation
If a logic 1 is present at the output of a two-input NOR gate, it means that both of its inputs must be at logic 0. This is because a NOR gate produces a logic 1 output only when both of its inputs are at logic 0. If any of the inputs are at logic 1, the output will be at logic 0. Therefore, for a logic 1 output, both inputs must be at logic 0.
18.
A NOR gate with both inputs inverted becomes a:
Correct Answer
C. OR gate
Explanation
When both inputs of a NOR gate are inverted, it means that the original inputs are negated. Since a NOR gate gives a high output only when both inputs are low, negating the inputs will result in a low output only when both inputs are high. This behavior is the same as an OR gate, where the output is high if any of the inputs are high. Therefore, a NOR gate with both inputs inverted becomes an OR gate.
19.
The logic symbol shown is for:
Correct Answer
B. NOR gate
Explanation
The logic symbol shown represents a NOR gate. A NOR gate is a digital logic gate that operates as an OR gate followed by a NOT gate. It produces a high output only when all of its inputs are low. In the given options, the symbol does not match the symbols for a NAND gate or an OR gate. Therefore, the correct answer is a NOR gate.
20.
Atoms that contain an equal number of protons and electrons are called:
Correct Answer
C. Neutral atoms
Explanation
Neutral atoms are atoms that contain an equal number of protons and electrons. Protons have a positive charge, while electrons have a negative charge. Since the number of protons and electrons in a neutral atom is equal, the positive and negative charges cancel each other out, resulting in a net charge of zero. This means that neutral atoms have no overall charge and are neither positively charged (positive ions) nor negatively charged (negative ions).
21.
Matter containing atoms with 3 or less valence electrons in their orbital paths are classified as:
Correct Answer
A. Conductors
Explanation
Matter containing atoms with 3 or less valence electrons in their orbital paths are classified as conductors. Conductors are materials that have a high electrical conductivity, meaning they allow the flow of electric current easily. This is because atoms with few valence electrons have loosely bound electrons that can move freely through the material, creating a pathway for the flow of electric charge.
22.
The maximum number of electrons that can exist in the valence shell is:
Correct Answer
C. 8
Explanation
The valence shell is the outermost shell of an atom, and it determines the atom's reactivity and ability to form chemical bonds. The maximum number of electrons that can exist in the valence shell is 8, known as the octet rule. This is because the valence shell can hold a maximum of 8 electrons to achieve a stable electron configuration, except for the first shell which can only hold 2 electrons.
23.
What are the 2 energy bands associated with most solids?
Correct Answer
B. Conduction...valence
Explanation
Most solids have two energy bands associated with them: the conduction band and the valence band. The conduction band is the band of energy levels that are accessible to electrons, allowing them to move freely and conduct electricity. On the other hand, the valence band is the band of energy levels that are occupied by valence electrons, which are responsible for the bonding between atoms in the solid. The forbidden band refers to the energy gap between the conduction and valence bands, where no energy levels are present.
24.
Which atomic bonding is commonly associated with insulator materials?
Correct Answer
C. Ionic
Explanation
Ionic bonding is commonly associated with insulator materials. In ionic bonding, electrons are transferred between atoms, creating positive and negative ions that are held together by electrostatic forces. Insulator materials have a large energy gap between their valence and conduction bands, which prevents the movement of electrons and inhibits the flow of electricity. Ionic compounds, such as salts, typically have high melting and boiling points and do not conduct electricity in their solid state, making them good insulators.
25.
Trivalent impurties are added to intrinsic materials to manufacture:
Correct Answer
B. P-type materials
Explanation
Trivalent impurities are added to intrinsic materials to manufacture P-type materials. In P-type materials, the impurities introduce extra valence electrons, creating an excess of positive charge carriers known as "holes." This results in a material that has a higher concentration of positive charge carriers than negative charge carriers, making it P-type.
26.
Neutrons have ________ charge.
Correct Answer
C. Mass but no
Explanation
Neutrons have mass but no charge. Unlike protons, which have a positive charge, and electrons, which have a negative charge, neutrons are electrically neutral. However, they do have mass, which contributes to the overall mass of an atom.
27.
The process of adding impurities to pure semiconductor materials is called:
Correct Answer
C. Doping
Explanation
Doping is the process of intentionally adding impurities to pure semiconductor materials. This is done to alter the electrical properties of the material, such as conductivity or the ability to conduct electricity. By introducing impurities, known as dopants, into the crystal lattice of the semiconductor, the number of free charge carriers can be increased or decreased, allowing for the control of electrical behavior. Doping is a crucial technique in the production of various electronic devices, such as transistors and diodes.
28.
When a neutral atom loses a valence electron it becomes:
Correct Answer
B. Positively charged
Explanation
When a neutral atom loses a valence electron, it becomes positively charged. This is because the atom now has more protons than electrons, resulting in an overall positive charge. The loss of an electron creates an imbalance in the atom's charge, making it positively charged.
29.
Atoms that contain 8 valence electrons make good:
Correct Answer
B. Insulator materials
Explanation
Atoms that contain 8 valence electrons make good insulator materials because they have a full outer electron shell. This stability prevents the free movement of electrons, making it difficult for electricity to flow through the material. Insulators are materials that do not conduct electricity well and are used to prevent the flow of electrical current.
30.
When a diode is forward biased, the majority charge carriers are pushed:
Correct Answer
A. Toward each other
Explanation
When a diode is forward biased, the majority charge carriers, which are the electrons in the N-type material and the holes in the P-type material, are pushed towards each other. This happens because the positive terminal of the battery is connected to the P-type material and the negative terminal is connected to the N-type material. The positive terminal repels the holes in the P-type material, while the negative terminal repels the electrons in the N-type material. As a result, the majority charge carriers move towards the junction between the N-type and P-type materials, where they recombine, allowing current to flow through the diode.
31.
The N material in a diode forms the _____ of the diode.
Correct Answer
B. Cathode
Explanation
The N material in a diode forms the cathode of the diode. In a diode, the cathode is the terminal that emits electrons or allows current to flow out of the device. The N material is doped with impurities to create an excess of free electrons, which makes it the cathode. The other terminal, known as the anode, is typically made of P material and has an excess of holes or positive charge carriers.
32.
The depletion region in a diode is void of:
Correct Answer
A. Majority charge carriers
Explanation
The depletion region in a diode is void of majority charge carriers. When a diode is in its forward biased state, the majority charge carriers (either electrons or holes) flow freely through the diode. However, when the diode is in its reverse biased state, the depletion region is formed. This region is created by the immobile ions in the p-n junction and is void of majority charge carriers. Therefore, the correct answer is majority charge carriers.
33.
Zener diodes are generaly operated:
Correct Answer
C. In their reverse bias mode
Explanation
Zener diodes are generally operated in their reverse bias mode. This is because Zener diodes are specifically designed to operate in this mode and take advantage of the Zener breakdown phenomenon. When a Zener diode is reverse biased, it allows a controlled amount of current to flow in the reverse direction, while maintaining a relatively constant voltage across its terminals. This makes Zener diodes useful for voltage regulation and protection against voltage spikes or transients. In contrast, using Zener diodes in their forward bias mode would not utilize their unique characteristics and would not provide the desired voltage regulation.
34.
When testing a diode, if the positive meter lead is connected to the cathode, and the negative meter lead is connected to the anode, the meter will read:
Correct Answer
C. Open circuit
Explanation
When testing a diode, if the positive meter lead is connected to the cathode and the negative meter lead is connected to the anode, the meter will read "open circuit". This means that there is no continuity or connection between the two leads, indicating that the diode is not conducting current in the forward bias condition. In an open circuit, the resistance is very high, preventing the flow of current through the diode.
35.
Which diode operates in a negative resistance region?
Correct Answer
A. Tunnel diode
Explanation
A tunnel diode operates in a negative resistance region. This means that as the voltage across the diode increases, the current flowing through it decreases. This is due to the quantum mechanical phenomenon known as tunneling, where electrons can pass through energy barriers that would normally be insurmountable. The unique characteristics of the tunnel diode make it useful in applications such as high-frequency oscillators and amplifiers.
36.
A diode is considered forward biased when the:
Correct Answer
A. Anode is (+) and cathode is (-)
Explanation
A diode is considered forward biased when the anode is positively charged and the cathode is negatively charged. In forward bias, the positive terminal of the power supply is connected to the anode, and the negative terminal is connected to the cathode. This configuration allows current to flow through the diode, as the positive voltage on the anode repels the majority charge carriers towards the junction, reducing the size of the depletion region.
37.
The area where the P and N materials are joined together is called the:
Correct Answer
B. P-N junction
Explanation
The area where the P and N materials are joined together is called the P-N junction. This junction forms a boundary between the two different types of semiconductor materials, creating a region with unique electrical properties. It is at this junction where the majority carriers from each material combine and recombine, allowing for the flow of current in one direction while blocking it in the opposite direction. The P-N junction is a key component in various electronic devices, such as diodes and transistors.
38.
An increase in temperature will cause a diode to:
Correct Answer
A. Increase current flow
Explanation
An increase in temperature will cause a diode to increase current flow because temperature affects the conductivity of the diode's semiconductor material. As the temperature rises, more charge carriers are generated, resulting in increased current flow. This phenomenon is known as thermal runaway, where the diode becomes more conductive as it gets hotter. Therefore, the diode's current flow will increase with an increase in temperature.
39.
The minority charge carrier in the N material is:
Correct Answer
B. The hole
Explanation
In N-type material, which is doped with impurities that have extra electrons, the majority charge carriers are electrons. However, there are also some missing electrons called holes, which act as minority charge carriers. These holes are created when the impurity atoms donate their extra electrons to the material. Therefore, the correct answer is "the hole."
40.
Which section of the BJT is generally doped the heaviest?
Correct Answer
B. Emitter
Explanation
The emitter section of a BJT is generally doped the heaviest. This is because the emitter is responsible for injecting majority charge carriers (electrons or holes) into the base region to facilitate the transistor action. By heavily doping the emitter, the concentration of majority charge carriers is increased, allowing for efficient injection into the base and amplification of the input signal.
41.
Generally, the ____ section is very narrow.
Correct Answer
A. Base
Explanation
The given correct answer is "base". In a transistor, the base section is typically very narrow compared to the emitter and collector sections. The base is responsible for controlling the flow of current between the emitter and the collector. It acts as a gatekeeper, allowing or blocking the flow of electrons. Its narrowness allows for precise control over the current flow, making it an essential part of the transistor's operation.
42.
Which transistor configuration inverts and amplifies the incoming signal?
Correct Answer
B. Common emitter
Explanation
The common emitter transistor configuration inverts and amplifies the incoming signal. In this configuration, the input signal is applied to the base terminal, while the output is taken from the collector terminal. The emitter terminal is common to both input and output. When the input signal is positive, the output signal becomes negative, and vice versa. Additionally, the common emitter configuration provides high voltage gain and moderate current gain, making it suitable for amplification purposes.
43.
Which transistor configuration amplifies the incoming signal without inverting it?
Correct Answer
A. Common base
Explanation
The common base transistor configuration amplifies the incoming signal without inverting it. In this configuration, the input is applied to the emitter and the output is taken from the collector. The base current controls the collector current, and due to the input being applied to the emitter, the output signal is in phase with the input signal. Therefore, the common base configuration provides non-inverting amplification.
44.
On a PNP transistor, if the base is made more positive than the emitter, the device will:
Correct Answer
C. Turn off
Explanation
When the base of a PNP transistor is made more positive than the emitter, it creates a reverse bias between the base and emitter junction. This reverse bias prevents the flow of current through the transistor, causing it to turn off. Therefore, the correct answer is "turn off."
45.
Which of the leads shown in the figure is the collector?
Correct Answer
A. Lead A
Explanation
In the given figure, lead A is the collector. The collector lead is responsible for collecting the majority charge carriers in a transistor. In a bipolar junction transistor, the collector region is typically the largest and is doped to have a lower concentration of charge carriers compared to the emitter and base regions. This allows the collector to attract and collect the majority charge carriers from the base region. Therefore, lead A is the correct answer for the collector lead.
46.
Which of the leads shown in the figure is the emitter?
Correct Answer
C. Lead C
Explanation
Based on the given information, the emitter lead can be identified as lead C.
47.
Which junction of the transistor must be forward biased for the device to turn ON?
Correct Answer
C. Emitter-base
Explanation
The emitter-base junction of the transistor must be forward biased for the device to turn ON. When the emitter-base junction is forward biased, it allows the flow of current from the emitter to the base, enabling the transistor to conduct and function properly.
48.
When the transistor is ON, the _______ current is always greater than the collector current.
Correct Answer
B. Emitter
Explanation
When the transistor is ON, the emitter current is always greater than the collector current. This is because the emitter current is the sum of the base current and the collector current. The base current controls the flow of current from the emitter to the collector, and typically only a small fraction of the emitter current flows through the base. Therefore, the emitter current is always greater than the collector current in an ON transistor.
49.
When the base-emitter junction is forward biased, the base-collector junction is:
Correct Answer
B. Reverse biased
Explanation
When the base-emitter junction is forward biased, it means that the base terminal is at a higher potential than the emitter terminal. In this case, the base-collector junction is reverse biased, meaning that the collector terminal is at a higher potential than the base terminal. This biasing arrangement allows for proper functioning of a transistor, as it establishes the necessary conditions for amplification and control of current flow.
50.
What are the two basic types of transistors?
Correct Answer
C. BJT & FET
Explanation
The two basic types of transistors are BJT (Bipolar Junction Transistor) and FET (Field Effect Transistor). BJT is a type of transistor that uses both electron and hole charge carriers, while FET is a type of transistor that uses only one type of charge carrier, either electrons or holes. Both BJT and FET are widely used in electronic devices for amplification and switching purposes.