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 outermost electrons in an atom's electron cloud, and they are responsible for the atom's ability to bond with other atoms. In the case of conductors, atoms with fewer valence electrons are more likely to easily lose or share electrons, allowing the flow of electric current. Therefore, atoms with 3 valence electrons are more likely to be good conductors.
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 outermost shell, also known as the valence shell, is considered to be complete when it contains eight electrons. This configuration is known as the octet rule and is commonly observed in noble gases, which are known for their stability. Having a complete outer shell allows the atom to have a lower energy state and be less likely to react with other atoms to gain or lose electrons.
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. Dielectrics are commonly used in capacitors and other electronic devices to store and control electrical energy. Unlike conductors, which allow the flow of electric charges, insulators prevent or greatly reduce the flow of charges. Therefore, the correct answer for this question is insulators.
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 is the measure of a material's ability to conduct electric current, voltage is the potential difference between two points in a circuit, and valence refers to the combining capacity of an atom.
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 that exerts a force on free electrons. It is the measure of electric potential energy per unit charge and is responsible for the flow of electric current in a circuit. Conductivity is a property that determines how well a material can conduct electricity, current is 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. It is a property of a material that opposes the flow of electric current. When resistance is increased, the current flow decreases, and when resistance is decreased, the current flow increases. Therefore, by adjusting the resistance in a circuit, the amount of current flowing through it 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 is the same throughout the circuit. To calculate the current, we can use Ohm's Law, which states that current (I) equals 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 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 flowing through all the components is the same. 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 the voltage across each branch is the same as the total voltage in the circuit.
10.
Source current in a parallel circuit will be divided according to branch
Correct Answer
D. Resistances
Explanation
In a parallel circuit, the source current will be divided among the different branches based on their resistances. Each branch offers a different amount of resistance to the flow of current. The branch with lower resistance will allow more current to pass through it, while the branch with higher resistance will allow less current to pass through it. This division of current is determined by the relative resistance values of each branch in the circuit. Therefore, the correct answer is resistances.
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, there are two branches with different voltages and currents. To find the resistance of each branch, we can use Ohm's law: R1 = V1/I1 and R2 = V2/I2. Plugging in the values, we get R1 = 440V/4A = 110 ohms and R2 = 440V/16A = 27.5 ohms. Adding the reciprocals of these resistances gives us 1/Rt = 1/110 + 1/27.5 = 0.009 + 0.036 = 0.045. Taking the reciprocal of this sum, we get Rt = 1/0.045 = 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 flowing through the parallel portion of the circuit remains the same. This is because the current has multiple paths it can take in the parallel portion, but the total current entering the parallel portion must be equal to the total current leaving it. On the other hand, in the series portion of the circuit, the current divides according to the component resistance. This is because the current has only one path to flow through in the series portion, and the components in that portion offer different levels of resistance, causing the current to divide accordingly.
13.
What is the total current in a series-parallel circuit that has a total voltage or 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. In this case, the series current is given as 6 amps (a) and one branch current is given as 2a. To find the total current, we need to add these two currents together, resulting in 6a. Therefore, the correct answer is 6a.
14.
The area around a magnet where its influence can be felt is the definition of the
Correct Answer
C. Magnetic field
Explanation
A magnet creates a magnetic field around itself, which is the region where its influence can be felt. This field is responsible for the attraction or repulsion of other magnets or magnetic materials. The saturation principle refers to the maximum magnetic field strength that a material can achieve. Magnetic theory is a broad term that encompasses various principles and concepts related to magnets. The law of attraction and repulsion is a general principle that describes how magnets interact with each other. Therefore, the correct answer is magnetic field.
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. This phenomenon occurs due to the alignment of magnetic domains within the material, which causes it to retain a magnetic field. Residual magnetism is commonly observed in permanent magnets and is important in various applications such as in the storage of data on hard drives and in the functioning 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 permeability of the material, which determines how easily the magnetic field can pass through it. 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 through electromechanical means, a conductor is necessary. A conductor is a material that allows the flow of electric current. When there is relative motion between a magnetic field and a conductor, it induces a voltage in the conductor due to electromagnetic induction. This voltage can be generated only if there is a complete circuit, which allows the flow of current. Therefore, a conductor is an essential component for electromechanical voltage generation.
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 motion requires more mechanical energy, 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 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. It refers to the production of an electromotive force (emf) in a conductor when it is exposed to a changing magnetic field. This process involves the movement of the conductor through the magnetic field or the variation of the magnetic field around the conductor. By utilizing electromagnetic induction, generators can convert mechanical energy into electrical energy, which is the basis for 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 creates a magnetic field around it. This magnetic field stores energy, which can be released when the current changes. This property of inductors allows them to oppose changes in current, making them useful in applications such as filters, transformers, and energy storage systems.
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 by which a current change in one coil induces a voltage in another coil. This occurs when the changing magnetic field produced by the current in the first coil passes through the second coil, creating an electromotive force (EMF) and inducing a current in the second coil. This phenomenon is widely used in the operation of transformers and is essential for the transmission of electrical energy over long distances.
22.
A transformer will change all of the following except
Correct Answer
A. Power
Explanation
A transformer is a device that is used to transfer electrical energy from one circuit to another through electromagnetic induction. It consists of two coils, known as the primary and secondary coils, which are wound around a common iron core. The primary coil is connected to a power source, and the secondary coil is connected to the load. The transformer operates based on the principle of mutual induction, where a changing current in the primary coil induces a voltage in the secondary coil. Therefore, a transformer can change the voltage and current levels between the primary and secondary circuits. However, it does not change the power, as power is the product of voltage and current.
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 receives the electrical energy from the power source and transfers it to the secondary winding through electromagnetic induction. The primary winding typically has a higher number of turns compared to the secondary winding to step up or step down the voltage as required.
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 small electrical current to control a larger electrical current. When the small current is applied to the relay, it activates an electromagnet, which then switches the larger current on or off. This makes a relay a useful component in various electrical systems, as it allows for the control of high-power circuits with low-power signals. Therefore, the correct answer is switch.
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 position even after the initial energizing signal is removed. It requires a separate signal to be sent to the second coil in order to reset the contacts to their original positions. Latching relays are commonly used in applications where it is important to maintain a specific state or position until intentionally changed.
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 creates an electric field between its plates. This electric field stores energy in the form of separated charges on the plates. The energy is stored in the electric field until it is discharged. This property of capacitors makes them useful in various electronic circuits for storing and releasing energy as needed.
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 conductive plates of the capacitor. It helps to increase the capacitance of the capacitor by reducing the electric field between the plates. The dielectric material acts as an insulator, preventing the flow of electric current between the plates while allowing the storage of electrical energy in the form of an electric field.
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 an AC voltage is applied to a capacitor, it charges and discharges, causing the flow of current to be out of phase with the voltage. This opposition to the flow of current is called capacitive reactance. It is measured in ohms and depends on the frequency of the AC signal and the capacitance of the capacitor. Capacitive reactance decreases with increasing frequency and increasing capacitance.
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 in a circuit is one of the factors that determine the time required to charge a capacitor. Resistance limits the flow of current in the circuit, so a higher resistance will result in a slower charging time for the capacitor. This is because the resistance restricts the flow of electrons, reducing the rate at which the capacitor can accumulate charge. Therefore, a larger amount of resistance in the circuit will increase the time it takes to charge the capacitor.
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 steady 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 applying a voltage across the diode to either forward bias or reverse bias it, which in turn expands or contracts the depletion region within the diode. 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
When a diode is placed in reverse bias, it allows only a small leakage current to flow through it. This makes it effective in protecting the circuit from voltage spikes or surges. When a spike or surge occurs, the diode quickly conducts and redirects the excess voltage away from the circuit, preventing damage to the components. Therefore, a diode in reverse bias acts as a spike protector.
32.
A zener will conduct in reverse bias
Correct Answer
C. Once the avalanche point has been reached
Explanation
A zener diode is designed to operate in reverse bias. It conducts a small current until the avalanche point is reached, which is the point where the diode starts to break down and conduct a larger current. Once the avalanche point is reached, the zener diode will continue to conduct in reverse bias and maintain a constant voltage across its terminals, even if the current increases. Therefore, the statement "once the avalanche point has been reached" correctly explains when a zener diode will conduct 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 place a resistor in series with it. This is because the resistor helps to limit the current flowing through the zener diode and prevent it from getting damaged due to excessive current. By placing the resistor in series, the current flowing through both the resistor and the zener diode is the same, ensuring that the zener diode operates within its specified current range. Therefore, placing the resistor in series is the correct configuration for using a zener diode as a regulator.
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 of the LED and the negative terminal is connected to the cathode. In this configuration, current flows freely through the LED, allowing it to emit light. The forward biasing causes the electrons and holes to recombine at the junction of the LED, releasing energy in the form of photons, which results 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
An LED typically operates at an approximate voltage of 1.6 volts. This voltage is necessary to overcome the forward voltage drop across the diode junction and allow current to flow through the LED, causing it to emit light. The specific voltage may vary depending on the type and color of the LED, but 1.6 volts is a commonly accepted value for many LEDs.
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. The SCR is a four-layer, three-terminal semiconductor device that acts as a switch. It consists of three PN junctions: the anode-cathode junction, the anode-gate junction, and the cathode-gate junction. The anode-cathode junction is the main junction through which current flows when the SCR is forward-biased. The anode-gate and cathode-gate junctions are used to control the SCR's conduction by applying a small current to the gate terminal. Therefore, the correct answer is three.
37.
A silicon controlled rectifier (SCR) is mainly used as
Correct Answer
D. An electronic switch
Explanation
An SCR, or silicon controlled rectifier, is a semiconductor device that can control the flow of current in a circuit. It acts as an electronic switch, allowing current to flow when a small control current is applied to its gate terminal. This makes it useful for various applications where precise control of current flow is required, such as in power electronics, motor control, and lighting systems. It is not primarily used as a fuse, spike protection, or circuit breaker, although it may offer some level of protection in certain situations.
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 controls the flow of current between the emitter and base terminals. By applying a small current or voltage to the base terminal, the emitter-base junction can be forward biased or reverse biased, which in turn controls the larger current flowing between the emitter and collector terminals. This junction acts as a control element in the transistor, allowing it to amplify or switch signals.
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. Forward biasing allows current to flow from the emitter to the base, which is necessary for the transistor to function properly. This biasing arrangement ensures that the transistor is in its active region, where it can amplify and control the current flowing through it.
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 provides the main path for current flow in a transistor. In this circuit, the emitter is connected to the positive terminal of the power supply, while the collector is connected to the negative terminal. The emitter-collector circuit allows current to flow from the emitter to the collector, controlling the output of the transistor. The other options, such as the emitter-base circuit and base-collector circuit, also play important roles in transistor operation, but they do not provide the main path for current flow.
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 controlling the flow of current in the UJT. The tab is usually connected to the emitter lead to provide a convenient point for heat dissipation. This allows the UJT to operate at optimal temperatures and ensures its proper functioning.
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 and represents the ratio of the peak voltage across the UJT to the valley voltage. This ratio determines the amount of voltage required to forward bias the UJT and activate its conduction.
43.
What component uses voltage to control the size of the current flow channel?
Correct Answer
D. FET
Explanation
A Field-Effect Transistor (FET) is a component that uses voltage to control the size of the current flow channel. When a voltage is applied to the gate terminal of a FET, it creates an electric field that controls the conductivity of the channel between the source and drain terminals. By varying the voltage applied to the gate, the size of the current flow channel can be adjusted, allowing for precise control of the current flowing through the FET. This makes FETs widely used in applications such as amplifiers, switches, and voltage regulators.
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 an FET. The arrow indicates the direction of the flow of these charge carriers, 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 that is not electrically connected to the rest of the device. The gate of a MOSFET is insulated from the channel by a thin layer of oxide, allowing for control of the flow of current through the device. This isolation of the gate from the rest of the device allows for high input impedance and low power consumption, making MOSFETs suitable for a wide range of applications in electronics.
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 induced by applying a voltage to the gate, allowing current to flow between the source and drain. Unlike other types of FETs, there is no direct physical connection between the source and drain in an induced channel MOSFET.
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. This device is designed to protect electrical circuits from voltage surges by acting as a voltage-dependent resistor. When the voltage across the MOV exceeds its threshold, it conducts current and diverts the excess voltage away from the circuit, protecting the sensitive components. The two semiconductors in the MOV are typically made of zinc oxide, which provides the necessary nonlinear voltage-current characteristics required for surge protection.
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 a logical and organized approach to problem-solving. It helps to identify the root cause of the issue by breaking it down into smaller steps and systematically testing each component or variable. This method ensures that all possible causes are considered and eliminates the need for guesswork or random attempts to fix the problem. It saves time and resources by providing a structured framework for problem-solving, leading to more efficient and effective troubleshooting.
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, showing the relationships between its components and how they are connected. It provides a simplified and organized view of the system, making it easier to understand and troubleshoot. By looking at a schematic, one can quickly identify the different parts of the system and their functions, helping to promote a better understanding of how the system works and how to diagnose and fix any issues that may arise.
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 is designed to aid you if you see an unfamiliar symbol. It provides a list or index of reference designations used in a schematic or wiring diagram, allowing you to quickly identify and understand the meaning of unfamiliar symbols. This index helps in locating the relevant information or component in the diagram, making troubleshooting easier and more efficient.