1.
How many valence electrons are needed to make a good conductor?
Correct Answer
A. 3
Explanation
A good conductor requires only 3 valence electrons. Valence electrons are the electrons in the outermost energy level of an atom, and they are responsible for the atom's ability to form bonds and participate in chemical reactions. In the case of conductors, having fewer valence electrons allows for easier movement of electrons, which is necessary for the material to conduct electricity effectively. Therefore, a material with 3 valence electrons would be more likely to be a good conductor compared to materials with 4, 5, or 6 valence electrons.
2.
An atom with eight electrons in its outermost shell is said to be
Correct Answer
B. Stable
Explanation
An atom with eight electrons in its outermost shell is said to be stable. This is because the octet rule states that atoms tend to gain, lose, or share electrons in order to achieve a full outer shell of eight electrons, which is the most stable configuration. Having a full outer shell allows the atom to have a lower energy state and be less likely to react with other atoms. Therefore, an atom with eight electrons in its outermost shell is considered stable.
3.
"Dielectric" is the term used for
Correct Answer
B. Insulators
Explanation
The term "dielectric" is used to refer to insulators. Insulators are materials that do not conduct electricity easily and have high resistance to the flow of electric current. They are commonly used to separate conductive materials and prevent the flow of electricity between them. Dielectrics are often used in capacitors, where they store electrical energy by creating an electric field. Unlike conductors, which allow the free flow of electrons, insulators keep electrons tightly bound to their atoms, limiting the movement of charge.
4.
"The flow or drift of electrons through a conductor" in the same direction at the same time is the definition of
Correct Answer
C. Current
Explanation
Current is the correct answer because it refers to the flow or drift of electrons through a conductor in the same direction at the same time. Conductivity refers to the ability of a material to conduct electricity, voltage refers to the electric potential difference between two points, and valence refers to the combining power of an element.
5.
The potential difference between two points in a circuit that exerts a force on free electrons is called
Correct Answer
B. Voltage
Explanation
Voltage is the correct answer because it refers to the potential difference between two points in a circuit. It is the force that pushes free electrons and causes them to move. Conductivity refers to the ability of a material to conduct electricity, current refers to the flow of electric charge, and valence refers to the combining capacity of an element.
6.
What is used to control current flow in a circuit?
Correct Answer
C. Resistance
Explanation
Resistance is used to control current flow in a circuit. Resistance is a measure of how much a material or component opposes the flow of electric current. It is measured in ohms (Ω). When resistance is increased in a circuit, it limits the amount of current that can flow through it. Conversely, when resistance is decreased, more current can flow. Therefore, by adjusting the resistance in a circuit, the current flow can be controlled.
7.
Given a voltage of 24 volts and a resistance of 18 ohms in a series circuit, the current through the resistor would be
Correct Answer
B. 1.33 amps
Explanation
In a series circuit, the current passing through each component is the same. To calculate the current, we can use Ohm's Law, which states that current (I) is equal to voltage (V) divided by resistance (R). In this case, the voltage is 24 volts and the resistance is 18 ohms. Therefore, the current through the resistor would be 24 volts divided by 18 ohms, which equals approximately 1.33 amps.
8.
Total current in a series circuit is equal to the
Correct Answer
A. Current through one component
Explanation
In a series circuit, the current is the same throughout all components. This is because the current has only one path to flow through. Therefore, the total current in a series circuit is equal to the current through one component.
9.
In a parallel circuit, the total voltage is equal to the
Correct Answer
C. Voltage across each branch
Explanation
In a parallel circuit, the total voltage is equal to the sum of the voltages across each branch. This means that each branch in a parallel circuit has the same voltage across it.
10.
Source current in a parallel circuit will be divided according to branch
Correct Answer
D. Resistances
Explanation
In a parallel circuit, the current will divide among the different branches based on the resistance of each branch. This is because the branch with lower resistance will allow more current to flow through it compared to the branch with higher resistance. Therefore, the statement that the source current in a parallel circuit will be divided according to resistances is correct.
11.
What is the total resistance of a parallel circuit with branch voltages of 440 volt (v) and 440v and branch currents of 4 amp (a) and 16a?
Correct Answer
B. 22 ohms
Explanation
In a parallel circuit, the total resistance is calculated using the formula 1/Rt = 1/R1 + 1/R2 + 1/R3 + ... In this case, we have two branches with different voltages and currents. To find the resistance of each branch, we can use Ohm's law: R = V/I. For the first branch, R1 = 440v/4a = 110 ohms. For the second branch, R2 = 440v/16a = 27.5 ohms. Adding the reciprocals of these resistances gives 1/Rt = 1/110 + 1/27.5. Simplifying this equation gives Rt = 22 ohms.
12.
Total current in a series-parallel circuit remains the same throughout the
Correct Answer
B. Series part of the circuit and divides according to branch resistance in the parallel portion
Explanation
In a series-parallel circuit, the total current remains the same throughout the parallel portion of the circuit. This means that the current flowing through each branch in the parallel portion is equal. However, in the series portion of the circuit, the current divides according to the component resistance. This means that the current flowing through each component in the series portion is different and depends on the resistance of that component. Therefore, the correct answer is that the total current in a series-parallel circuit remains the same throughout the parallel portion of the circuit and divides according to branch resistance in the series portion.
13.
What is the total current in a series-parallel circuit that has a total voltage of 48 volts (v), a series current of 6 amps (a), one branch current of 2a, and the other branch resistance of 3 ohms?
Correct Answer
B. 6a
Explanation
In a series-parallel circuit, the total current is equal to the sum of the currents in each branch. Given that the series current is 6 amps and one branch current is 2 amps, the other branch current can be found by subtracting the series current from the total current. So, the other branch current is 6 amps - 2 amps = 4 amps. Therefore, the total current in the circuit is 2 amps + 4 amps = 6 amps.
14.
The area around a magnet where its influence can be felt is the definition of the
Correct Answer
C. Magnetic field
Explanation
A magnetic field refers to the area around a magnet where its influence can be felt. It is the region in which magnetic forces are exerted on other objects or magnets. Magnetic fields are created by moving electric charges, such as the flow of current in a wire or the movement of electrons within an atom. The strength and direction of the magnetic field are determined by the properties of the magnet and the distance from it.
15.
The magnetism that remains after the magnetizing force has been removed is known as
Correct Answer
D. Residual magnetism
Explanation
Residual magnetism refers to the magnetism that remains in a material even after the magnetizing force has been removed. It occurs due to the alignment of magnetic domains within the material. This phenomenon is commonly observed in permanent magnets, where the alignment of the domains creates a magnetic field that persists even without an external magnetic field. Residual magnetism is important in various applications, such as in the operation of electric motors and generators.
16.
The magnetic field of an electromagnet can be varied by changing the
Correct Answer
D. All of the above
Explanation
The magnetic field of an electromagnet can be varied by changing the type of core, the number of turns in the coil, and the amount of current through the coil. The type of core affects the magnetic permeability, which determines how easily the magnetic field lines pass through the core material. Increasing the number of turns in the coil increases the strength of the magnetic field. Finally, increasing the amount of current flowing through the coil increases the strength of the magnetic field according to Ampere's law. Therefore, all of these factors can be used to vary the magnetic field of an electromagnet.
17.
The electromechanical generation of a voltage requires a magnetic field, relative motion, and
Correct Answer
B. A conductor
Explanation
In order to generate a voltage electromechanically, a conductor is required. A conductor is a material that allows the flow of electric current. When the conductor moves relative to a magnetic field, it induces a voltage in the conductor through electromagnetic induction. This voltage can then be used to power a circuit or perform work. Therefore, a conductor is an essential component for the electromechanical generation of a voltage.
18.
In a simple generator, which would be the most difficult method to increase the output?
Correct Answer
B. Increase the amount of motion
Explanation
Increasing the amount of motion would be the most difficult method to increase the output in a simple generator. This is because increasing the amount of motion would require additional mechanical energy input, which can be challenging to achieve. On the other hand, increasing the area of the conductor, the strength of the magnetic field, or the relative resistance can be relatively easier to accomplish and can result in a higher output.
19.
The principle behind all electromechanical generation is
Correct Answer
D. Electromagnetic induction
Explanation
Electromagnetic induction is the principle behind all electromechanical generation. This process involves the generation of electric current in a conductor by varying the magnetic field around it. When a conductor is exposed to a changing magnetic field, it induces a voltage, which in turn produces an electric current. This phenomenon is used in various electrical generators, such as turbines, to convert mechanical energy into electrical energy. Therefore, electromagnetic induction is the correct principle behind electromechanical generation.
20.
An inductor stores energy in the form of
Correct Answer
C. A magnetic field
Explanation
An inductor stores energy in the form of a magnetic field. When current flows through an inductor, it generates a magnetic field around it. This magnetic field stores energy, which can be released when the current changes. This property of inductors makes them useful in various applications, such as in power supplies, transformers, and electric motors.
21.
The process by which a current change in one coil produces a voltage in another coil is called
Correct Answer
C. Mutual induction
Explanation
Mutual induction is the process in which a current change in one coil induces a voltage in another coil. This occurs when the magnetic field created by the changing current in the first coil passes through the second coil, causing a voltage to be induced. This phenomenon is commonly used in transformers and is the basis for the operation of many electrical devices. Inductance refers to the property of a coil to oppose changes in current, while self-induction specifically refers to the voltage induced in the same coil where the current is changing.
22.
A transformer will change all of the following except
Correct Answer
A. Power
Explanation
A transformer is a device that is used to change the voltage of an alternating current (AC) electrical supply. It works based on the principle of electromagnetic induction. When an AC current flows through the primary coil of the transformer, it creates a changing magnetic field which induces a voltage in the secondary coil. This voltage can be higher or lower than the input voltage, depending on the turns ratio of the transformer. However, a transformer does not change the power of the electrical supply. Power is the product of voltage and current, and since the transformer only changes the voltage and not the current, the power remains constant.
23.
Normally, the winding of a transformer that is connected to a power source is known as the
Correct Answer
B. Primary winding
Explanation
The winding of a transformer that is connected to a power source is known as the primary winding. This is because the primary winding is responsible for receiving the input power from the source and transferring it to the secondary winding, which then delivers the transformed output power. The primary winding typically has a higher number of turns compared to the secondary winding in order to step up or step down the voltage as required by the transformer.
24.
A relay is an electrically operated
Correct Answer
C. Switch
Explanation
A relay is an electrically operated switch. It is a device that allows a low-power signal to control a high-power circuit. When the relay receives an electrical signal, it activates an electromagnet that opens or closes the switch contacts. This allows the relay to control the flow of electricity in a circuit, making it an essential component in many electrical systems.
25.
A relay that once energized, requires a second coil to be energized before the contacts will return to their original positions is called a
Correct Answer
B. Latching relay
Explanation
A relay that once energized, requires a second coil to be energized before the contacts will return to their original positions is called a latching relay. This type of relay is designed to "latch" or hold its state even after the initial signal is removed. It requires a separate signal or coil to reset the relay back to its original position. Latching relays are commonly used in applications where it is necessary to maintain a specific state until a reset signal is received.
26.
A capacitor stores energy in the form of
Correct Answer
D. An electrostatic field
Explanation
A capacitor stores energy in the form of an electrostatic field. When a voltage is applied across the capacitor, it causes a separation of charge, with one plate accumulating positive charge and the other accumulating negative charge. This separation of charge creates an electric field between the plates, which stores energy. The energy is released when the capacitor is discharged, as the charges flow back together and the electric field collapses. This stored energy can be used in various electronic circuits and devices.
27.
In a capacitor, the dielectric is the
Correct Answer
C. Insulator
Explanation
In a capacitor, the dielectric is the insulator. The dielectric is a non-conductive material that is placed between the two plates of the capacitor to prevent the flow of electric current between them. It helps to increase the capacitance of the capacitor by storing more electric charge. The dielectric material can be made of various substances such as ceramic, plastic, or paper. It acts as a barrier, allowing the electric field to pass through but blocking the flow of electrons.
28.
Opposition of a capacitor to alternating current (AC) is called
Correct Answer
C. Capacitive reactance
Explanation
Capacitive reactance is the opposition of a capacitor to alternating current (AC). When AC voltage is applied to a capacitor, it charges and discharges, causing a phase shift between the voltage and current. This opposition to the flow of current is known as capacitive reactance. It is measured in ohms and is inversely proportional to the frequency of the AC signal. As the frequency increases, the capacitive reactance decreases, allowing more current to flow through the capacitor.
29.
The factors which determine the time required to charge a capacitor are the capacitance and the
Correct Answer
C. Amount of resistance
Explanation
The amount of resistance is a factor that determines the time required to charge a capacitor. Resistance limits the flow of current in the circuit, and a higher resistance will result in a slower charging time for the capacitor. This is because the resistance restricts the amount of current that can flow into the capacitor, causing it to charge at a slower rate. Therefore, the amount of resistance in the circuit affects the time it takes for the capacitor to reach its full charge.
30.
Expanding or contracting the depletion region of a diode is called
Correct Answer
D. Biasing
Explanation
Biasing refers to the process of applying a voltage or current to a device such as a diode in order to establish the desired operating conditions. In the case of a diode, biasing involves either expanding or contracting the depletion region, which is the region devoid of free charge carriers. This adjustment of the depletion region allows for controlling the flow of current through the diode, making it an essential aspect of diode operation. Therefore, the correct answer is biasing.
31.
A diode placed in a circuit in reverse bias is being used as
Correct Answer
A. A spike protector
Explanation
A diode placed in reverse bias acts as a spike protector because it allows current to flow only when the voltage across it exceeds a certain threshold, known as the breakdown voltage. In this configuration, the diode prevents voltage spikes by diverting excessive voltage away from sensitive components in the circuit. When a voltage spike occurs, the diode conducts and provides a low resistance path for the excess voltage, protecting the circuit from potential damage.
32.
A zener will conduct in reverse bias
Correct Answer
C. Once the avalanche point has been reached
Explanation
A zener diode conducts in reverse bias once the avalanche point has been reached. The avalanche point is the point at which the reverse voltage across the diode is high enough to cause a breakdown in the diode's structure. Once this point is reached, the zener diode starts conducting in reverse bias and allows current to flow through it. This behavior is useful in voltage regulation applications, where the zener diode can maintain a constant voltage across a load by conducting excess current in reverse bias.
33.
A zener being used as a regulator must have a resistor placed in the circuit in
Correct Answer
A. Series
Explanation
When a zener diode is used as a regulator, it is necessary to have a resistor placed in series with it. This resistor helps to limit the current flowing through the zener diode and prevents it from being damaged due to excessive current. By placing the resistor in series, the current through the zener diode is controlled, ensuring that it operates within its specified limits. This allows the zener diode to regulate the voltage effectively and maintain a stable output voltage.
34.
A Light Emitting Diode (LED) produces light when it is
Correct Answer
C. Forward biased
Explanation
When a Light Emitting Diode (LED) is forward biased, it means that the positive terminal of the power supply is connected to the anode (the longer leg) of the LED, and the negative terminal is connected to the cathode (the shorter leg). In this configuration, current flows from the anode to the cathode, allowing the LED to produce light. This is because forward biasing creates a forward voltage across the LED, causing the electrons and holes to recombine and emit photons, resulting in the production of light.
35.
What is the approximate operating voltage of a Light Emitting Diode (LED)?
Correct Answer
C. 1.6 volts
Explanation
The approximate operating voltage of a Light Emitting Diode (LED) is 1.6 volts. LED is a semiconductor device that emits light when an electric current passes through it. It requires a specific voltage to function properly, and in the case of an LED, it is approximately 1.6 volts. This voltage is necessary to activate the LED and generate the desired light output.
36.
The Silicon Controlled Rectifier (SCR) has how many PN junctions?
Correct Answer
C. Three
Explanation
The Silicon Controlled Rectifier (SCR) has three PN junctions. A PN junction is formed when a P-type semiconductor material is joined with an N-type semiconductor material. In the case of an SCR, there are three layers of alternating P-type and N-type materials, resulting in three PN junctions. These junctions play a crucial role in the operation of the SCR, allowing it to control the flow of current in a circuit.
37.
An Silicon Controlled Rectifier (SCR) is mainly used as
Correct Answer
D. An electronic switch
Explanation
An SCR, or Silicon Controlled Rectifier, is primarily used as an electronic switch. It can control the flow of current in a circuit by acting as a gate that allows or blocks the current. This makes it useful in various applications where precise control of electrical power is required, such as in motor control, lighting control, and power supply regulation. Unlike a fuse, spike protection, or a circuit breaker, which are primarily used for protection against overcurrent or voltage spikes, an SCR is specifically designed to function as a switch in electronic circuits.
38.
The control junction of a transistor is the
Correct Answer
A. Emitter-base junction
Explanation
The control junction of a transistor is the emitter-base junction because it plays a crucial role in controlling the flow of current through the transistor. The emitter-base junction is forward-biased, allowing current to flow from the emitter to the base region. By varying the voltage at the base, the current flow can be controlled, making the emitter-base junction the control junction of the transistor.
39.
In normal operation, the emitter-base junction of a transistor is
Correct Answer
B. Forward biased
Explanation
The emitter-base junction of a transistor is forward biased during normal operation. This means that the emitter terminal is at a higher potential than the base terminal, allowing current to flow from the emitter to the base. This forward biasing is essential for the transistor to function properly and amplify signals. It helps in controlling the flow of current between the emitter and collector terminals, allowing the transistor to act as a switch or amplifier in electronic circuits.
40.
The transistor circuit that provides the main path for current flow is the
Correct Answer
D. Emitter-collector circuit
Explanation
The emitter-collector circuit is the transistor circuit that provides the main path for current flow. In this circuit, the emitter terminal is connected to the power supply, while the collector terminal is connected to the load. When a small current flows into the base terminal, it controls the much larger current flowing from the emitter to the collector. This configuration allows the transistor to amplify signals and act as a switch. The emitter-collector circuit is commonly used in applications such as amplifiers and digital logic circuits.
41.
The tab on the case of a Unijunction Transistor (UJT) indicates the
Correct Answer
C. Emitter lead
Explanation
The tab on the case of a Unijunction Transistor (UJT) indicates the emitter lead. The emitter lead is responsible for emitting the majority charge carriers in the UJT. The tab is usually connected to the emitter lead to provide a convenient way to identify and connect it in the circuit.
42.
What determines the amount of potential required to forward bias a Unijunction Transistor (UJT)?
Correct Answer
D. Intrinsic stand-off ratio
Explanation
The amount of potential required to forward bias a Unijunction Transistor (UJT) is determined by its intrinsic stand-off ratio. The intrinsic stand-off ratio is a characteristic of the UJT that determines the ratio of the peak voltage at the emitter junction to the peak voltage at the base junction. This ratio determines the amount of potential required to forward bias the UJT and activate its operation. Therefore, the intrinsic stand-off ratio is the factor that determines the amount of potential required for forward biasing a UJT.
43.
What component uses voltage to control the size of the current flow channel?
Correct Answer
D. FET
Explanation
A FET (Field-Effect Transistor) is a component that uses voltage to control the size of the current flow channel. FETs have three terminals: source, gate, and drain. By applying a voltage to the gate terminal, the electric field generated controls the conductivity of the channel between the source and drain terminals. This voltage-controlled behavior of FETs makes them suitable for various applications, including amplification and switching in electronic circuits.
44.
In a field-effect transistor (FET) symbol, the arrow always points to the
Correct Answer
B. N-type material
Explanation
The arrow in a field-effect transistor (FET) symbol always points to the N-type material. This is because the N-type material is the source of majority charge carriers (electrons) in the FET. The arrow indicates the direction of electron flow, which is from the N-type material to the P-type material in an FET.
45.
Which semi-conductor device has a gate that is not electrically connected to the rest of the device?
Correct Answer
C. MOSFET
Explanation
A MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is a type of semiconductor device that has a gate which is not electrically connected to the rest of the device. The gate of a MOSFET is isolated from the channel by a thin layer of oxide, hence the name. This isolation allows for better control of the current flow through the device, making it a popular choice in many electronic applications. In contrast, an SCR (Silicon-Controlled Rectifier), JFET (Junction Field-Effect Transistor), and UJT (Unijunction Transistor) all have gates that are electrically connected to the rest of the device.
46.
Which type of field-effect transistor (FET) has no built-in connection between the source and drain?
Correct Answer
D. Induced channel MOSFET
Explanation
The induced channel MOSFET is the type of field-effect transistor (FET) that has no built-in connection between the source and drain. In this type of FET, the channel is formed by the induced charge carriers in the substrate, and there is no physical connection between the source and drain regions. This allows for better control of the channel and reduces leakage current. JFET, IGFET, and dual-gate MOSFET all have a built-in connection between the source and drain.
47.
A Metal Oxide Varistor (MOV) is made up of how many semi-conductors?
Correct Answer
A. 2
Explanation
A Metal Oxide Varistor (MOV) is made up of two semiconductors. The MOV is a voltage-dependent resistor that is commonly used to protect electrical devices from high voltage surges. It consists of a ceramic disc made of metal oxides, such as zinc oxide, which acts as a semiconductor. The two semiconductors within the MOV allow it to have a high resistance when the voltage across it is low, and a low resistance when the voltage exceeds a certain threshold. This characteristic helps to divert excess voltage away from sensitive electronic components, protecting them from damage.
48.
The best method of troubleshooting is the
Correct Answer
A. Systematic method
Explanation
The systematic method is the best method of troubleshooting because it involves following a step-by-step approach to identify and solve problems. This method ensures that all possible causes are considered and tested systematically, leading to a more efficient and effective troubleshooting process. It helps to eliminate guesswork and reduces the chances of missing any potential solutions. By following a systematic approach, troubleshooting becomes more organized and structured, increasing the likelihood of finding the root cause of the problem and implementing the appropriate solution.
49.
Which troubleshooting aid is designed to promote understanding of the system?
Correct Answer
B. Schematic
Explanation
A schematic is a visual representation of a system or process, showing the relationships between different components. It helps promote understanding by providing a clear and concise overview of how the system works. By using symbols and labels, a schematic allows technicians to easily identify and troubleshoot any issues that may arise. It provides a comprehensive view of the system's structure and connections, making it an effective troubleshooting aid for promoting understanding.
50.
Which troubleshooting aid is designed to aid you if you see an unfamiliar symbol?
Correct Answer
D. Reference designation index
Explanation
A reference designation index is a troubleshooting aid that helps when encountering unfamiliar symbols. It provides a comprehensive list of symbols used in a specific system or diagram, allowing the user to quickly identify and understand the meaning of the symbol they are unfamiliar with. This index serves as a reference guide, enabling efficient troubleshooting and problem-solving by providing clear and concise explanations for each symbol used.