2A672 Volume 1 Ure
Unit Review Questions from CDC 2A672 Volume 1
- 1.
What is the simplest form of matter?
- A.
Element
- B.
Mixture
- C.
Electrons
- D.
Compound
Correct Answer
A. ElementExplanation
An element is the simplest form of matter because it consists of only one type of atom. Atoms are the basic building blocks of matter, and elements are made up of identical atoms. They cannot be broken down into simpler substances by chemical means. In contrast, mixtures are combinations of different substances, compounds are made up of two or more elements, and electrons are subatomic particles that are part of atoms. Therefore, the correct answer is element.Rate this question:
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- 2.
In an atom, what electrons contain the most energy?
- A.
The energy is shared equally by all electrons
- B.
Orbiting electrons
- C.
Valence electrons
- D.
K shell electrons
Correct Answer
C. Valence electronsExplanation
Valence electrons are the electrons located in the outermost energy level of an atom. These electrons have the highest energy because they are farther away from the nucleus and experience less attraction from the positive charge of the protons. As a result, valence electrons are more easily involved in chemical reactions and are responsible for the formation of chemical bonds.Rate this question:
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- 3.
Atoms having more than four electrons, but less than eight are known as
- A.
Insulators
- B.
Conductors
- C.
Stable atoms
- D.
Semiconductors
Correct Answer
A. InsulatorsExplanation
Atoms having more than four electrons, but less than eight are known as insulators. Insulators are materials that do not conduct electricity easily because their outermost electron shells are full, making it difficult for electrons to move freely. These atoms have enough electrons to form stable electron configurations, but not enough to participate in the conduction of electricity. Therefore, they do not allow the flow of electric current and are considered insulators.Rate this question:
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- 4.
The electrostatic fields around a positive ion move
- A.
Inward
- B.
Outward
- C.
Inward, then outward
- D.
Outward, then inward
Correct Answer
B. OutwardExplanation
The electrostatic fields around a positive ion move outward. Positive ions have an excess of positive charge, which causes the surrounding electric field lines to radiate away from the ion. This outward movement of electric field lines is a result of the repulsion between positive charges. Therefore, the correct answer is outward.Rate this question:
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- 5.
What are factors that affect the resistance of a material?
- A.
Area, weight, and state of material
- B.
Area, temperature, and type of material
- C.
Temperature, weight, and state of material
- D.
Temperature, type of material, and state of material
Correct Answer
B. Area, temperature, and type of materialExplanation
The factors that affect the resistance of a material are the area, temperature, and type of material. The area of the material affects resistance because a larger area allows for more current to flow through, decreasing resistance. Temperature affects resistance because as temperature increases, the resistance of the material also increases. The type of material affects resistance because different materials have different resistivities, which determines how easily they allow current to flow through. Therefore, the correct answer is area, temperature, and type of material.Rate this question:
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- 6.
What is the resistance in a circuit if the power rating is 40 watts and total current is 2 amps?
- A.
40 ohms
- B.
20 ohms
- C.
10 ohms
- D.
0.5 ohms
Correct Answer
C. 10 ohmsExplanation
40/2^2 = 40/4 = 10 ohmsRate this question:
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- 7.
Convert 500 milliamps to standard amperage.
- A.
.005 amps
- B.
.05 amps
- C.
.5 amps
- D.
50 amps
Correct Answer
C. .5 ampsExplanation
To convert milliamps to standard amperage, you divide the value by 1000. In this case, 500 milliamps divided by 1000 equals 0.5 amps. Therefore, the correct answer is .5 amps.Rate this question:
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- 8.
In a series-parallel circuit, find RT if series resistor R1 = 7 ohms, and parallel resistors R2 and R3 = 8 ohms.
- A.
23 ohms
- B.
15 ohms
- C.
11 ohms
- D.
8 ohms
Correct Answer
C. 11 ohmsExplanation
Find RT of parallel resistors: RT = 8x8/8+8 = 64/16 = 4
New R2 is RT of parallel resistors. Now use RT = R1 (7) + R2 (4) = 11 ohmsRate this question:
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- 9.
In a series-parallel circuit, the series current at I1 = 9 amps; in the two parallel branches, I2 = 5 amps; and the value of I3 is not listed. Use Ohms's law to find the value of I3 and IT.
- A.
I3 = 5 amps and IT = 14 amps
- B.
I3 = 4 amps and IT = 9 amps
- C.
I3 = 4 amps and IT =18 amps
- D.
Not enough information to solve
Correct Answer
B. I3 = 4 amps and IT = 9 ampsExplanation
Total current is equal throughout series part of circuit. So since I1 (in series part) = 9 amps, IT = 9 amps. Parallel branches always add up to equal current flow in series part. So, I2 (5 amps) + I3 (?) = 9 amps. I3 has to equal 4 amps.Rate this question:
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- 10.
What is the difference between and open and a short?
- A.
An open causes resistance to decrease; a short causes resistance to increase
- B.
Excessive current flow in an open circuit; no current flow in a shorted component
- C.
No current flow in an open circuit; excessive current flow in a shorted component
- D.
Minimum voltage development across the open component; maximum voltage development across the shorted component
Correct Answer
C. No current flow in an open circuit; excessive current flow in a shorted componentExplanation
An open circuit refers to a break or discontinuity in the circuit, which prevents the flow of current. As a result, there is no current flow in an open circuit. On the other hand, a short circuit occurs when there is an unintended connection between two points in the circuit with low resistance. This causes excessive current flow as it bypasses the intended path. Therefore, the given answer correctly states that there is no current flow in an open circuit, while there is excessive current flow in a shorted component.Rate this question:
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- 11.
Voltage induced into a conductor by the expanding and collapsing of a magnetic field is
- A.
Magnetism
- B.
Reluctance
- C.
Direct current
- D.
Electromagnetic induction
Correct Answer
D. Electromagnetic inductionExplanation
Electromagnetic induction refers to the process of generating an electric current in a conductor by varying the magnetic field around it. When a magnetic field expands or collapses, it creates a change in the magnetic flux through the conductor, which in turn induces a voltage. This phenomenon is the basis for many important applications, such as generators, transformers, and induction coils. Therefore, electromagnetic induction is the correct answer to the question.Rate this question:
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- 12.
In an inductor, what happens to the magnetic lines of force if the diameter of the core is increased in size?
- A.
Permeability increases
- B.
Magnetic field decreases
- C.
Induction of the coil increases
- D.
Induction of the coil decreases
Correct Answer
C. Induction of the coil increasesExplanation
When the diameter of the core in an inductor is increased, it allows for more magnetic lines of force to pass through the coil. This results in an increase in the induction of the coil. The larger diameter of the core provides a larger area for the magnetic field to interact with, leading to a stronger magnetic field and increased induction.Rate this question:
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- 13.
What is the basic principle of operation for transformers?
- A.
Mutual induction
- B.
Magnetic induction
- C.
Counterelectromotive force
- D.
Primary and secondary induction
Correct Answer
A. Mutual inductionExplanation
The basic principle of operation for transformers is mutual induction. Mutual induction refers to the process in which a changing current in one coil induces a voltage in a nearby coil. In a transformer, this principle is utilized to transfer electrical energy between two or more coils without direct electrical connection. The primary coil, connected to an alternating current source, creates a changing magnetic field which induces a voltage in the secondary coil. This allows for the transformation of voltage levels, either stepping up or stepping down the voltage, depending on the number of turns in each coil.Rate this question:
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- 14.
What type of transformer contains more turns in the primary winding than in the secondary winding?
- A.
Current
- B.
Step up
- C.
Rectifier
- D.
Step down
Correct Answer
D. Step downExplanation
A step-down transformer contains more turns in the primary winding than in the secondary winding. This type of transformer is used to decrease the voltage from the primary side to the secondary side. By having fewer turns in the secondary winding, the voltage is reduced while the current is increased. This allows for the transformation of high voltage, low current power to low voltage, high current power, which is often used in household appliances and electronic devices.Rate this question:
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- 15.
If the size of the plates of a capacitor is increased, how is capacitance affected?
- A.
Capacitance increases
- B.
Capacitance decreases
- C.
Electrons are distorted and scattered
- D.
Electrostatic force between the plates decreases
Correct Answer
A. Capacitance increasesExplanation
When the size of the plates of a capacitor is increased, the capacitance increases. This is because capacitance is directly proportional to the area of the plates and inversely proportional to the distance between them. By increasing the size of the plates, the area increases, leading to an increase in capacitance.Rate this question:
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- 16.
What statement best describes a capacitive circuit?
- A.
Current leads applied voltage by 90 degrees
- B.
Applied voltage leads current by 90 degrees
- C.
Has the ability to conduct in one direction and not in the other
- D.
Has the ability to conduct in all directions when gated or discharged
Correct Answer
A. Current leads applied voltage by 90 degreesExplanation
A capacitive circuit is characterized by the fact that the current leads the applied voltage by 90 degrees. This means that the current reaches its maximum value before the voltage does. Capacitors store energy in an electric field and release it when the voltage across them changes. As the voltage increases, the current begins to flow, but it takes some time for the current to reach its maximum value. Therefore, the current leads the voltage in a capacitive circuit.Rate this question:
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- 17.
How many electrons does the valance band of an intrinsic semiconductor have?
- A.
3
- B.
4
- C.
5
- D.
6
Correct Answer
B. 4Explanation
The valence band of an intrinsic semiconductor has 4 electrons. In an intrinsic semiconductor, the valence band is fully occupied by electrons, and it represents the highest energy level of electrons that are bound to atoms in the crystal lattice. Each atom in the lattice contributes one valence electron, and since there are typically four valence electrons per atom in a semiconductor material, the valence band is filled with 4 electrons.Rate this question:
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- 18.
What are the minority carriers in P-type material?
- A.
Holes
- B.
Protons
- C.
Neutrons
- D.
Electrons
Correct Answer
D. ElectronsExplanation
In P-type material, the majority carriers are holes, which are positively charged. However, the minority carriers are electrons, which are negatively charged. These electrons are present in small quantities in P-type material and are responsible for the conduction of electric current.Rate this question:
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- 19.
The area of a semiconductor where P-type material is joined to N-type material is known as
- A.
Dielectric region
- B.
Depletion region
- C.
Depletion field
- D.
PN region
Correct Answer
B. Depletion regionExplanation
The area where P-type material is joined to N-type material in a semiconductor is known as the depletion region. This region is formed due to the diffusion of majority carriers from each region into the other. As a result, the region becomes depleted of majority carriers and forms a region with a high concentration of immobile ions. This depletion region creates a potential barrier that prevents further flow of majority carriers, thus acting as a barrier between the P and N regions in a semiconductor device.Rate this question:
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- 20.
A junction diode has how many PN junction(s)?
- A.
1
- B.
2
- C.
3
- D.
4
Correct Answer
A. 1Explanation
A junction diode has one PN junction. A PN junction is formed when a P-type semiconductor and an N-type semiconductor are brought together. This junction is the key component of a diode and allows the flow of current in only one direction. Therefore, a junction diode has only one PN junction.Rate this question:
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- 21.
In a circuit using a bridge rectifier, how many diodes are forward biased during the first cycle of alternating current (AC)?
- A.
4
- B.
3
- C.
2
- D.
1
Correct Answer
C. 2Explanation
In a bridge rectifier circuit, there are four diodes arranged in a bridge configuration. During the first cycle of alternating current (AC), two diodes are forward biased, which means they conduct current in the forward direction. The other two diodes are reverse biased and do not conduct current. Therefore, the correct answer is 2.Rate this question:
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- 22.
If a zener diode is installed in the forward bias mode in a circuit, it acts as a
- A.
Regular diode
- B.
Spike protector
- C.
Voltage reference
- D.
Voltage regulator
Correct Answer
A. Regular diodeExplanation
When a zener diode is installed in the forward bias mode in a circuit, it acts as a regular diode. In forward bias, the diode allows current to flow through it, just like a regular diode. However, unlike a regular diode, a zener diode is specifically designed to operate in the reverse bias mode. In reverse bias, a zener diode exhibits a unique behavior known as the zener breakdown, where it maintains a constant voltage across its terminals regardless of the current flowing through it. But when a zener diode is forward biased, it does not exhibit this zener breakdown behavior and functions like a regular diode.Rate this question:
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- 23.
How is a zener diode connected in a circuit to regulate voltage?
- A.
In parallel to the load
- B.
In series with the load
- C.
In parallel to the resistor
- D.
In series with the resistor
Correct Answer
A. In parallel to the loadExplanation
A zener diode is connected in parallel to the load in order to regulate voltage. When connected in this manner, the zener diode acts as a voltage regulator by maintaining a constant voltage across the load, regardless of variations in the input voltage. This is achieved by allowing current to flow through the zener diode in the reverse bias direction, which causes it to breakdown and maintain a constant voltage drop.Rate this question:
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- 24.
If a schematic diagram doesn't list a reference for the zener diode, the diode is probably being used as a
- A.
Reference
- B.
Normal diode
- C.
Spike protector
- D.
Voltage regulator
Correct Answer
C. Spike protectorExplanation
If a schematic diagram doesn't list a reference for the zener diode, it is likely being used as a spike protector. A zener diode is a type of diode that is designed to operate in the reverse breakdown region, where it exhibits a controlled breakdown voltage. This makes it useful for protecting circuits from voltage spikes or transients by diverting excess voltage away from sensitive components. Therefore, if the zener diode is not specifically referenced in the schematic diagram, it is likely being used as a spike protector.Rate this question:
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- 25.
How is the zener diode connected in a circuit to protect the load?
- A.
In parallel to the resistor
- B.
In series with the load
- C.
In parallel to the load
- D.
Forward biased
Correct Answer
C. In parallel to the loadExplanation
The zener diode is connected in parallel to the load in order to protect it. When the voltage across the load exceeds the breakdown voltage of the zener diode, the zener diode starts conducting and limits the voltage across the load to the breakdown voltage. This ensures that the load is protected from excessive voltage and prevents any damage that could occur.Rate this question:
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- 26.
What is the primary use of a silicon-controlled rectifier (SCR)?
- A.
Electronic switch
- B.
Voltage regulator
- C.
Circuit amplifier
- D.
Spike protector
Correct Answer
A. Electronic switchExplanation
A silicon-controlled rectifier (SCR) is primarily used as an electronic switch. It is a semiconductor device that can control the flow of electric current in a circuit. When triggered, it allows current to flow in one direction, similar to a diode. SCR's are commonly used in applications such as motor control, power supplies, and lighting dimmers, where they can efficiently control the flow of high-power electrical signals. They are known for their ability to handle high voltage and current levels, making them suitable for switching applications.Rate this question:
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- 27.
The silicon-controlled rectifier (SCR) has how many layers?
- A.
1
- B.
2
- C.
3
- D.
4
Correct Answer
D. 4Explanation
The silicon-controlled rectifier (SCR) is a four-layer semiconductor device. It consists of three P-N junctions and four layers of alternating P and N-type material. The four layers are known as the anode, cathode, gate, and base. The SCR is used as a controlled switch for high-power applications and can only conduct current in one direction.Rate this question:
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- 28.
If a small potential is applied to the gate of a silicon-controlled rectifier (SCR), the
- A.
Middle junction of the SCR is reversed biased and the SCR turns off
- B.
Middle junction of the SCR is forward biased and the SCR turns on
- C.
Depletion region increases in size and blocks current flow
- D.
Depletion region decreases in size and stops current flow
Correct Answer
B. Middle junction of the SCR is forward biased and the SCR turns onExplanation
When a small potential is applied to the gate of a silicon-controlled rectifier (SCR), it causes the middle junction of the SCR to become forward biased. This means that the voltage at the gate is higher than the voltage at the cathode, allowing current to flow through the SCR. As a result, the SCR turns on and conducts current.Rate this question:
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- 29.
What is the major difference between an NPN transistor and a PNP transistor?
- A.
A PNP transistor can only be used as a regulator
- B.
An NPN transistor can only be used as a switch
- C.
Direction of current flow
- D.
Number of junctions
Correct Answer
C. Direction of current flowExplanation
The major difference between an NPN transistor and a PNP transistor is the direction of current flow. In an NPN transistor, the current flows from the emitter to the collector, while in a PNP transistor, the current flows from the collector to the emitter. This fundamental difference in current flow direction is what sets these two types of transistors apart and determines their specific applications and behaviors.Rate this question:
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- 30.
If the arrow in a bipolar transistor is pointing away from the base, what type of transister is it?
- A.
N-type
- B.
P-type
- C.
NPN
- D.
PNP
Correct Answer
C. NPNExplanation
If the arrow in a bipolar transistor is pointing away from the base, it indicates that the transistor is an NPN type. In an NPN transistor, the majority charge carriers are electrons, and the arrow signifies the direction of the electron flow. The arrow pointing away from the base indicates that the base is P-type and the emitter and collector are N-type.Rate this question:
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- 31.
The circuit in the bipolar transistor that carries 5 percent of the current flow is the
- A.
Basecircuit circuit
- B.
Load circuit
- C.
Control circuit
- D.
Emmiter-collector
Correct Answer
C. Control circuitExplanation
The control circuit in a bipolar transistor is responsible for regulating the flow of current. It determines the base current, which in turn controls the collector current. In this scenario, the control circuit is carrying 5 percent of the total current flow. This means that it is actively involved in controlling the transistor's operation and plays a crucial role in maintaining the desired current levels.Rate this question:
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- 32.
What happens if the emitter-base (E-B) current is increased in a transistor amplifier?
- A.
Resitance decreases and current through the load circuit decreases
- B.
Current decreases through the emitter-collector (E-C) circuit
- C.
Resistance increases and current flow decreases
- D.
Current increases through the E-C circuit
Correct Answer
D. Current increases through the E-C circuitExplanation
When the emitter-base (E-B) current is increased in a transistor amplifier, it causes the transistor to enter into a state of higher conduction. This leads to an increase in the current flowing through the emitter-collector (E-C) circuit. Therefore, the correct answer is that the current increases through the E-C circuit.Rate this question:
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- 33.
How many junctions are in a unijunction transister (UJT)?
- A.
1
- B.
2
- C.
3
- D.
4
Correct Answer
A. 1Explanation
A unijunction transistor (UJT) typically has one junction. It is a three-layered semiconductor device with a single pn junction. The UJT is commonly used in oscillator, timing, and triggering circuits due to its unique characteristics. The presence of a single junction allows for easy control of the device's behavior and makes it suitable for specific applications in electronic circuits.Rate this question:
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- 34.
What are the three leads in a unijunction transistor (UJT) called?
- A.
Anode, cathose, and gate
- B.
Emitter, base 1, and base 2
- C.
Emitter, collector, and base
- D.
Common emitter, common collector, and common base
Correct Answer
B. Emitter, base 1, and base 2Explanation
The three leads in a unijunction transistor (UJT) are called emitter, base 1, and base 2.Rate this question:
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- 35.
The emitter in a unijunction transister always points toward the
- A.
Base 1 lead
- B.
Collector
- C.
Emitter
- D.
Gate
Correct Answer
A. Base 1 leadExplanation
The emitter in a unijunction transistor always points toward the base 1 lead because the base 1 lead is the terminal that controls the operation of the transistor. The emitter is responsible for emitting the majority charge carriers (electrons or holes) into the base region, and by pointing towards the base 1 lead, it ensures that the control signal applied to the base 1 lead can modulate the emitter current effectively. This arrangement allows for proper operation and control of the unijunction transistor.Rate this question:
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- 36.
The amount of voltage it takes for a unijunction transistor (UJT) to fire is determined by the position
- A.
The emitter is placed on the N-type material
- B.
The emitter is placed on the P-type material
- C.
Of B1 and B2 on the P-type material
- D.
Of the UJT in the circuit
Correct Answer
A. The emitter is placed on the N-type materialExplanation
The correct answer is that the amount of voltage it takes for a unijunction transistor (UJT) to fire is determined by the position of the emitter on the N-type material. This is because the UJT is a three-layer semiconductor device, with a P-type material sandwiched between two N-type materials. The position of the emitter on the N-type material affects the electric field distribution within the device, which in turn determines the voltage required for the UJT to fire.Rate this question:
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- 37.
What controls the firing time of the unijunction transistor (UJT)?
- A.
Intrinsic standoff ratio
- B.
Resistance in the circuit
- C.
Capacitance in the circuit
- D.
Resistance and capacitance in the circuit
Correct Answer
D. Resistance and capacitance in the circuitExplanation
The firing time of the unijunction transistor (UJT) is controlled by the resistance and capacitance in the circuit. The resistance determines the charging and discharging time of the capacitor, while the capacitance determines the amount of charge stored in the capacitor. By adjusting the values of both resistance and capacitance, the firing time of the UJT can be controlled.Rate this question:
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- 38.
In what position must the line drop switch be placed when adjustments are made to a voltage regulator?
- A.
ON
- B.
OFF
- C.
Adjust
- D.
Regulator
Correct Answer
A. ONExplanation
The line drop switch must be placed in the ON position when adjustments are made to a voltage regulator. This is because the ON position allows the flow of current through the regulator, enabling adjustments to be made to the voltage output. The OFF position would cut off the current flow, making it impossible to make any adjustments. The Adjust and Regulator options are not relevant in this context.Rate this question:
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- 39.
What component of the voltage regulator compensates for losses in the power cable by sensing changes in current flow?
- A.
Load rheostat
- B.
No load rheostat
- C.
Line drop switch
- D.
Voltage adjustment rheostat
Correct Answer
A. Load rheostatExplanation
The load rheostat is the component of the voltage regulator that compensates for losses in the power cable by sensing changes in current flow. It adjusts the resistance in the circuit to maintain a stable voltage output despite variations in the current. This helps to ensure that the voltage reaching the load remains constant even if there are losses in the power cable.Rate this question:
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- 40.
The portion of the voltage regulator that supplies exciter field voltage is transformer
- A.
(T1) and rectifier (B3)
- B.
(T3) and rectifier (B2)
- C.
(T2) and rectifier (B1)
- D.
(T1) and rectifier (CR26)
Correct Answer
D. (T1) and rectifier (CR26)Explanation
The correct answer is (T1) and rectifier (CR26). The voltage regulator supplies exciter field voltage through a transformer (T1) and a rectifier (CR26). The transformer steps down the voltage to the desired level and the rectifier converts the AC voltage to DC voltage for the exciter field. This combination of transformer and rectifier is responsible for supplying the exciter field voltage in the voltage regulator.Rate this question:
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- 41.
Refer to foldout 1. After performing an ops check of the -86 generator set, you proceed to shut the unit down. After the generator stops, you notice the engine on light continues to glow. What is the probable cause of this trouble?
- A.
S46 open
- B.
S48 open
- C.
S46 closed
- D.
S48 closed
Correct Answer
D. S48 closedExplanation
The probable cause of the engine on light continuing to glow after shutting down the generator is that S48 is closed.Rate this question:
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