1.
What is the simplest form of matter?
Correct Answer
A. Element
Explanation
An element is the simplest form of matter because it consists of only one type of atom. It cannot be broken down into simpler substances by chemical reactions. Elements are the building blocks of all other substances and are represented by symbols on the periodic table. Examples of elements include oxygen, carbon, and gold.
2.
In an atom what electrons contain the most energy?
Correct Answer
C. Valence electrons
Explanation
Valence electrons are the electrons in the outermost energy level of an atom. These electrons have the highest energy because they are farther from the nucleus and experience less attraction. Valence electrons play a crucial role in chemical bonding and determining the reactivity of an atom. Therefore, they contain the most energy among the given options.
3.
If there are eight electrons in the outer most shell of an atom then it is considered?
Correct Answer
D. Stable
Explanation
If an atom has eight electrons in its outermost shell, it is considered stable. This is because the outermost shell, also known as the valence shell, is considered full when it contains eight electrons. This configuration is known as the octet rule and is typically found in noble gases, which are known for their stability. Having a full outer shell allows the atom to have a balanced charge and reduces its reactivity, making it less likely to form chemical bonds with other atoms.
4.
Atoms having more than four electrons, but less than eight are know as?
Correct Answer
A. Insulators
Explanation
Atoms having more than four electrons, but less than eight are known as insulators. This is because insulators have a completely filled valence shell, which makes it difficult for electrons to move freely and conduct electricity. Insulators are characterized by their high resistance to the flow of electric current.
5.
The electrostatic fields around a positive ion move
Correct Answer
B. Outward
Explanation
The electrostatic fields around a positive ion move outward. This is because positive ions have an excess of protons, which creates a positive charge. The positive charge repels other positive charges and attracts negative charges. As a result, the electrostatic fields spread outwards from the positive ion, creating a region of influence where other charges are affected. Therefore, the correct answer is outward.
6.
The force required to move free electrons through a conductor is known as?
Correct Answer
B. Voltage
Explanation
Voltage is the force required to move free electrons through a conductor. It is a measure of the electric potential difference between two points in a circuit. When a voltage is applied across a conductor, it creates an electric field that pushes the free electrons, causing them to move and create an electric current. Therefore, voltage is the correct answer in this case.
7.
What are factors that affect the resistance of a material?
Correct Answer
B. Area, temperature, and type of material
Explanation
The factors that affect the resistance of a material are the area, temperature, and type of material. The area of the material affects the resistance because a larger area allows for more current to flow through, reducing resistance. The temperature of the material affects the resistance because as the temperature increases, the resistance also increases. The type of material affects the resistance because different materials have different resistivities, which determine how easily current can flow through them.
8.
What is the resistance in a circuit if the power rating is 40 watts and the total current is 2 amps?
Correct Answer
C. 10 ohms
Explanation
The power rating of a circuit is given by the formula P = I^2 * R, where P is the power, I is the current, and R is the resistance. Rearranging the formula, we get R = P / I^2. Substituting the given values, we have R = 40 watts / (2 amps)^2 = 40 watts / 4 amps^2 = 10 ohms. Therefore, the resistance in the circuit is 10 ohms.
9.
In a series parallel circuit, find RT (total resistance) if series resistor R1 =7 ohms and parallel resistors R2 and R3=8 ohms?
Correct Answer
C. 11 ohms
Explanation
In a series-parallel circuit, the total resistance (RT) can be calculated by adding the resistances of the series resistors and the reciprocal of the sum of the reciprocals of the parallel resistors. In this case, the series resistor R1 has a resistance of 7 ohms. The parallel resistors R2 and R3 have a resistance of 8 ohms each. Therefore, the total resistance can be calculated as follows: 1/RT = 1/R1 + 1/R2 + 1/R3 = 1/7 + 1/8 + 1/8 = 23/56. Taking the reciprocal of both sides gives RT = 56/23, which is approximately 11 ohms.
10.
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 law to find the value of I3 and IT
Correct Answer
B. I3= 4 amps and IT= 9 amps
Explanation
In a series-parallel circuit, the total current (IT) is equal to the sum of the currents in the series branches. Therefore, IT = I1 + I3. Given that I1 = 9 amps, we can substitute this value into the equation to get IT = 9 + I3.
Additionally, in a parallel circuit, the current in each branch is the same. Therefore, I2 = I3. Given that I2 = 5 amps, we can substitute this value into the equation to get I3 = 5 amps.
Substituting the value of I3 into the equation for IT, we get IT = 9 + 5 = 14 amps. Therefore, the correct answer is I3 = 5 amps and IT = 14 amps.
11.
In a series parallel circuit, total voltage is 12 volts, the value of E1 in the series portion of the circuit is unknown. there are two parallel branches (E2=3 volts) and the value of E3 in the second parallel is unknown. using ohms law, find the value of E1 and E3
Correct Answer
D. E3=3 volts and E1= 9 volts
Explanation
In a series-parallel circuit, the total voltage across the circuit is equal to the sum of the voltages across each component. Since the total voltage is given as 12 volts, and the voltage across one of the parallel branches (E2) is given as 3 volts, the voltage across the other parallel branch (E3) can be found by subtracting E2 from the total voltage: E3 = 12 - 3 = 9 volts. Similarly, the voltage across the series portion of the circuit (E1) can be found by subtracting the voltage across the parallel branches (E3) from the total voltage: E1 = 12 - 9 = 3 volts. Therefore, the correct answer is E3 = 3 volts and E1 = 9 volts.
12.
What is the difference between an open and a short?
Correct Answer
C. No current flow in an open circuit; excessive current flow in a shorted component
Explanation
An open circuit refers to a break or interruption in the flow of current, resulting in no current flow. On the other hand, a short circuit occurs when there is a low resistance path that allows excessive current to flow. Therefore, the correct answer states that there is no current flow in an open circuit, while there is excessive current flow in a shorted component.
13.
When voltage is induced by a relative motion between the conductor and a magnetic field this principle is know as?
Correct Answer
D. Electromagnetic induction
Explanation
Electromagnetic induction is the correct answer because it refers to the principle where voltage is induced in a conductor when there is a relative motion between the conductor and a magnetic field. This phenomenon was first discovered by Michael Faraday in the early 19th century and is the basis for the operation of generators and transformers. It is a fundamental concept in electromagnetism and plays a crucial role in various electrical devices and technologies.
14.
In am inductive circuit what is meant by current lags voltage by 90 degrees?
Correct Answer
B. Current is maximum when voltage is zero; voltage is maximum when current is zero
Explanation
In an inductive circuit, current lags voltage by 90 degrees means that the maximum value of current occurs when the voltage is at its minimum value (zero), and the maximum value of voltage occurs when the current is at its minimum value (zero). This lagging relationship between current and voltage is a characteristic of inductive circuits, where the current takes time to reach its maximum value after the voltage has reached its maximum value.
15.
What is the basic principle of operation for transformers?
Correct Answer
A. Mutual induction
Explanation
The basic principle of operation for transformers is mutual induction. This refers to the process where a changing current in the primary coil induces a changing magnetic field, which in turn induces a voltage in the secondary coil. This allows for the transfer of electrical energy from one circuit to another without direct electrical connection.
16.
What transformer winding acts as a conductor and provides the path into which the voltage is induced?
Correct Answer
C. Secondary
Explanation
The secondary winding of a transformer acts as a conductor and provides the path into which the voltage is induced. When an alternating current flows through the primary winding, it creates a changing magnetic field. This changing magnetic field induces a voltage in the secondary winding, which is then used to transfer electrical energy to the load. Therefore, the secondary winding is responsible for carrying the induced voltage and delivering it to the connected circuit or device.
17.
If the size of the plates of a capacitor is increased how is capacitance affected?
Correct Answer
A. Capacitance increases
Explanation
When the size of the plates of a capacitor is increased, the distance between the plates decreases. This results in an increase in the capacitance of the capacitor. Capacitance is directly proportional to the area of the plates and inversely proportional to the distance between them. Therefore, when the size of the plates is increased, the capacitance increases.
18.
What statement best describes a capacitive circuit?
Correct Answer
A. Current leads applied voltage by 90 degrees
Explanation
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 peak value before the voltage does in a capacitive circuit. This behavior is due to the fact that capacitors store energy in an electric field and release it as the voltage across them changes. As the voltage increases, the capacitor charges and the current flows, but the current reaches its maximum value before the voltage does, resulting in a phase shift of 90 degrees.
19.
In what type of circuit(s) does a capacitor oppose any change in voltage
Correct Answer
D. AC
Explanation
A capacitor opposes any change in voltage in AC circuits because it stores and releases electrical energy in response to the alternating current. As the voltage in an AC circuit constantly changes direction, the capacitor charges and discharges accordingly, resisting any sudden changes in voltage. In DC circuits, a capacitor can also oppose changes in voltage to some extent, but it eventually reaches a steady state and allows the voltage to pass through. Therefore, the correct answer is AC.
20.
What statement best describes a diode?
Correct Answer
C. Has the ability to conduct in one direction and not the other
Explanation
A diode is a semiconductor device that allows current to flow in one direction and blocks it in the opposite direction. This property is known as rectification and is the fundamental function of a diode. When a positive voltage is applied to the anode and a negative voltage to the cathode, the diode conducts and allows current to flow. However, if the polarity is reversed, the diode becomes non-conductive and blocks the flow of current. This characteristic makes diodes useful in various applications such as rectifiers, voltage regulators, and signal demodulation.
21.
What are the minority carriers in a p-type material?
Correct Answer
D. Electrons
Explanation
In a p-type material, the majority carriers are holes, which are positively charged. Minority carriers, on the other hand, are the minority charge carriers in the material. In this case, the minority carriers in a p-type material are electrons. Electrons are negatively charged particles and in a p-type material, they are present in smaller numbers compared to the majority carriers (holes).
22.
The area of a semiconductor where p-type material is joined to n-type material is known as?
Correct Answer
B. Depletion region
Explanation
The area of a semiconductor where p-type material is joined to n-type material is known as the depletion region. This region is created due to the diffusion of charge carriers from one type of material to the other, resulting in a region that is depleted of majority carriers. The depletion region acts as a barrier to the flow of current in the absence of an external voltage or bias.
23.
A junction diode has how many PN junctions?
Correct Answer
A. 1
Explanation
A junction diode has only one PN junction. A PN junction is formed by joining a P-type semiconductor with an N-type semiconductor, creating a region where electrons and holes can recombine. This junction is responsible for the diode's ability to conduct current in one direction while blocking it in the opposite direction. Therefore, a junction diode has a single PN junction.
24.
If a negative potential is connected to the cathode and a positive potential is connected to the anode of a PN junction, the diode is?
Correct Answer
B. Forward biased
Explanation
When a negative potential is connected to the cathode and a positive potential is connected to the anode of a PN junction, it creates a forward bias. In this biasing condition, the diode allows current to flow from the anode to the cathode, enabling the diode to be forward biased. Therefore, the correct answer is "forward biased."
25.
In a circuit using a bridge rectifier how many diodes a forward biased during the first cycle of alternation current (AC)
Correct Answer
C. 2
Explanation
In a circuit using a bridge rectifier, there are two diodes that are forward biased during the first cycle of alternating current (AC). The bridge rectifier consists of four diodes arranged in a bridge configuration. During the positive half cycle of the AC input, two diodes become forward biased and allow current to flow through them, while the other two diodes become reverse biased and block the current. This arrangement ensures that the AC input is converted into a pulsating DC output. Therefore, the correct answer is 2.
26.
How is a zener diode connected in a circuit to regulate voltage?
Correct Answer
A. In parellel to the load
Explanation
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. It achieves this by allowing current to flow in the reverse direction when the voltage exceeds a certain threshold (known as the Zener voltage). This ensures that the voltage across the load remains stable, even if there are fluctuations in the input voltage.
27.
how is a zener diode connected in a circuit to protect the load?
Correct Answer
C. In parallel to the load
Explanation
A 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, it starts conducting and limits the voltage to the breakdown voltage. This prevents the load from being damaged by excessive voltage. By connecting the Zener diode in parallel to the load, it provides a low resistance path for the excess voltage, ensuring that the load receives a safe and regulated voltage.
28.
what is the primary use of silicon-controlled rectifier (SCR)
Correct Answer
A. Electronic switch
Explanation
The primary use of a silicon-controlled rectifier (SCR) is as an electronic switch. An SCR can control the flow of current in a circuit by acting as a switch that can be turned on or off. It is commonly used in applications where high power switching is required, such as in motor control, lighting control, and power supplies. By controlling the switching of the SCR, the flow of current can be regulated, making it an efficient and reliable electronic switch.
29.
The silicon-controlled rectifier (SCR) has how many layers?
Correct Answer
D. 4
Explanation
The silicon-controlled rectifier (SCR) has four layers. The SCR is a type of semiconductor device that acts as a switch for high-power electrical circuits. It consists of three P-N junctions and four layers of alternating P-type and N-type materials. The four layers are arranged in a specific order, with the middle layer acting as the control terminal. This layer structure allows the SCR to control the flow of current in a circuit, making it a useful component in various applications such as power control and voltage regulation.
30.
Question 30 / 88
in order to turn off a silcon-controlled rectifier (SCR) the current must drop below the?
Correct Answer
B. Holding current
Explanation
To turn off a silicon-controlled rectifier (SCR), the current must drop below the holding current. The holding current is the minimum current required to keep the SCR in the conducting state once it has been triggered. If the current falls below this threshold, the SCR will turn off and stop conducting. Therefore, the holding current is the correct answer for this question.
31.
What is the major difference between an NPN transistor and a PNP transistor?
Correct Answer
C. Direction of current flow
Explanation
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 collector to the emitter, while in a PNP transistor, the current flows from the emitter to the collector. This difference in current flow direction is due to the difference in the arrangement of the semiconductor materials and the polarity of the voltage applied to the transistor.
32.
If the arrow in a bipolar transistor is pointing away from the base, what type of transistor is it?
Correct Answer
C. NPN
Explanation
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 base is made of p-type material, and the emitter and collector are made of n-type material. The arrow represents the direction of conventional current flow, which is from the emitter to the base and then to the collector in an NPN transistor.
33.
The most positive point in a PNP bipolar transistor is the?
Correct Answer
C. Emitter
Explanation
The emitter of a PNP bipolar transistor is the most positive point because it is connected to the positive terminal of the power supply. It is responsible for injecting majority charge carriers (electrons in PNP transistors) into the base region, which allows current to flow from the collector to the emitter. The emitter current is controlled by the base current, and the collector current is a multiple of the emitter current. Therefore, the emitter plays a crucial role in the overall operation of the transistor.
34.
The circuit in the bipolar transistor that carries 5 percent of the current flow is the?
Correct Answer
C. Control circuit
Explanation
The control circuit in a bipolar transistor is responsible for regulating the flow of current in the transistor. It controls the amount of current that flows through the base terminal, which in turn controls the amplification and switching of the transistor. In this case, since the control circuit carries only 5 percent of the total current flow, it indicates that it has a smaller current compared to the other circuits. Therefore, the correct answer is the control circuit.
35.
What happens if the emitter-base (E-B) current is increased in a transistor amplifier?
Correct Answer
D. Current increases through the E-C circuit
Explanation
If the emitter-base (E-B) current is increased in a transistor amplifier, the current through the emitter-collector (E-C) circuit will increase. This is because the emitter-base current controls the current flow between the emitter and collector terminals of the transistor. By increasing the E-B current, more current will be allowed to flow through the E-C circuit. The other options are incorrect because they suggest that the current would decrease or that the resistance would change, which is not the case when the E-B current is increased.
36.
What are the three leads in a unijunction transistor (UJT) called?
Correct Answer
B. Emitter, base 1 and base 2
Explanation
The correct answer is emitter, base 1 and base 2. In a unijunction transistor (UJT), the emitter is the terminal from which the majority carriers are emitted, while base 1 and base 2 are the two terminals used to control the transistor's operation. Base 1 is used to control the voltage at which the transistor switches from high to low resistance, while base 2 is used to control the timing of the switching process. Thus, these three leads play crucial roles in the functioning of a UJT.
37.
The emitter in a unijunction transistor always points towards the?
Correct Answer
A. Base 1 lead
Explanation
The emitter in a unijunction transistor always points towards the base 1 lead. This is because the base 1 lead is the terminal that controls the flow of current in the device. The emitter is responsible for emitting the majority charge carriers, which then flow towards the base 1 lead. Therefore, the emitter needs to be positioned in a way that allows it to effectively control the current flow through the base 1 lead.
38.
What controls the firing time of the unijunction transistor?
Correct Answer
D. Resistance and capacitance in the circuit
Explanation
The firing time of a unijunction transistor is controlled by the resistance and capacitance in the circuit. The resistance determines the charging and discharging rate of the capacitor, while the capacitance determines the amount of charge that can be stored. Therefore, by adjusting the resistance and capacitance values, the firing time of the unijunction transistor can be controlled.
39.
a metal oxide varistor (MOV) is made up of how many semiconductors?
Correct Answer
A. 2
Explanation
An MOV is made up of two semiconductors. This is because a metal oxide varistor is a type of voltage-dependent resistor that consists of a ceramic disc made of zinc oxide. The zinc oxide disc acts as a semiconductor, and it is sandwiched between two metal electrodes. When a high voltage is applied across the MOV, it causes the zinc oxide to conduct electricity, thereby protecting the circuit from voltage surges. Therefore, an MOV is made up of two semiconductors, the zinc oxide disc, and the metal electrodes.
40.
What component of the voltage regulator compensates for loses in the power cable by sensing changes in the current flow?
Correct Answer
A. Load rheostat
Explanation
The load rheostat is the component of the voltage regulator that compensates for losses in the power cable by sensing changes in the current flow. It adjusts the resistance in the circuit to maintain a constant voltage output, compensating for any voltage drops caused by the power cable. This ensures that the desired voltage is delivered to the load, regardless of any losses in the cable.
41.
Which one do you like?
Correct Answer
A. Option 1