Interested In Electronics? Try This Quiz About AC Circuits

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  • 1/40 Questions

    A Farad is a measurement of what ?

    • Inductance
    • Capacitance
    • Reactance
    • Resistance
    • Impedance
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About This Quiz

The circuit that is excited using alternating source is called an AC Circuit. The alternating current (AC) is used for domestic and industrial purposes. In an AC circuit, the value of the magnitude and the direction of current and voltages is not constant, it changes at a regular interval of time.
Interested in Electronics? Try this Quiz about AC Circuits

Interested In Electronics? Try This Quiz About AC Circuits - Quiz

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  • 2. 

    In an AC circuit with only resistance the current is ?

    • Always in phase with the voltage

    • 180 out of phase with voltage

    • Leads the voltage by 180 degrees

    • Lags behind the voltage by 180 degrees

    • Peaked out

    Correct Answer
    A. Always in phase with the voltage
    Explanation
    In an AC circuit with only resistance, the current is always in phase with the voltage. This means that the current and voltage reach their maximum and minimum values at the same time. This is because in a purely resistive circuit, there is no reactance to cause a phase shift between the current and voltage. Therefore, the current and voltage waveforms are aligned and have the same frequency and shape.

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  • 3. 

    How many alternations form one complete cycle in an alternating current (AC) waveform?

    • 1

    • 2

    • 3

    • 4

    • 6

    Correct Answer
    A. 2
    Explanation
    In an alternating current (AC) waveform, one complete cycle consists of two alternations: one positive and one negative. Each alternation represents a half-cycle where the current flows in one direction, followed by a reversal in the next half-cycle. Thus, a full cycle includes both a positive and a negative alternation.

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  • 4. 

    Inductive reactance is measured in what ?

    • Impedance

    • Z

    • Series

    • Parallel

    • Ohms

    Correct Answer
    A. Ohms
    Explanation
    Inductive reactance is a measure of the opposition that an inductor presents to the flow of alternating current (AC). It is caused by the inductor's ability to store and release energy in the form of a magnetic field. Reactance is measured in ohms, which is the unit of electrical resistance. Therefore, the correct answer is "Ohms."

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  • 5. 

    In an inductive circuit what is the relationship of voltage and current ?

    • Current leads voltage

    • There is a phase shift

    • Voltage leads current

    • They are in phase

    • Reactance is created

    Correct Answer
    A. Voltage leads current
    Explanation
    In an inductive circuit, voltage leads current. This means that the voltage waveform reaches its peak before the current waveform reaches its peak. This is due to the presence of inductance in the circuit, which causes the current to lag behind the voltage. The phase shift between voltage and current in an inductive circuit is typically 90 degrees. This relationship can be observed in devices such as inductors and transformers.

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  • 6. 

    The period of a waveform is the inverse of what ?

    • Cycle

    • Peak

    • Frequency

    • Time

    • Hz

    Correct Answer
    A. Frequency
    Explanation
    The period of a waveform represents the time it takes for one complete cycle of the waveform to occur. Therefore, it is the inverse of the frequency, which measures the number of cycles per second. As frequency increases, the period decreases, and vice versa.

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  • 7. 

    What is the formula for capacitance reactance ?

    • XC = f x c

    • XC = 6.28 x f x t

    • XC = 1 / 6.28 x f x c

    • XC = 6.28 x f x c

    • XC = Square root (XC squared + X squared)

    Correct Answer
    A. XC = 1 / 6.28 x f x c
    Explanation
    The formula for capacitance reactance is XC = 1 / 6.28 x f x c. This formula is derived from the relationship between capacitance reactance (XC), frequency (f), and capacitance (c). The reciprocal of 6.28 (which is approximately equal to 2π) is used to calculate the reactance. By dividing 1 by the product of 6.28, frequency, and capacitance, we can determine the value of XC. This formula is commonly used in electrical and electronic circuits to calculate the reactance of a capacitor at a given frequency.

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  • 8. 

    What is the formula to find RMS voltage ?

    • RMS = Peak / .707

    • RMS = .707 x Peak

    • RMS = .637 x Peak

    • RMS = .077 x Peak

    • RMS = .7 X Peak

    Correct Answer
    A. RMS = .707 x Peak
    Explanation
    The formula to find RMS voltage is RMS = .707 x Peak. This formula is derived from the relationship between the RMS value and the peak value of a waveform. The value 0.707 is the square root of 2 divided by 2, which is a constant used to convert the peak value to the RMS value. By multiplying the peak value by 0.707, we can calculate the RMS voltage.

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  • 9. 

    Inductors in series are the same as ?

    • Resistors parallel

    • Capacitors is series

    • Overall impedance

    • Resistors in series

    • Lambda

    Correct Answer
    A. Resistors in series
    Explanation
    When inductors are connected in series, their total inductance adds up. This is similar to how resistors in series add up their resistances. In a series circuit, the total resistance or inductance is the sum of the individual values. Therefore, the correct answer is "Resistors in series".

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  • 10. 

    In a capacitance circuit what is the relationship of voltage and current ?

    • Current leads voltage

    • There is a phase shift

    • Voltage leads current

    • They are in phase

    • Reactance is created

    Correct Answer
    A. Current leads voltage
    Explanation
    In a capacitance circuit, the current leads the voltage. This means that the current reaches its peak value before the voltage does. This is because in a capacitor, the current flows in response to the changing voltage across it. As the voltage increases, the capacitor charges up and allows more current to flow. Therefore, the current reaches its peak value before the voltage does, resulting in a phase shift between the two.

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  • 11. 

    How does DC react to a capacitor ?

    • Voltage leads

    • Capacitance rises

    • It is blocked

    • Phase shift

    • Leakage

    Correct Answer
    A. It is blocked
    Explanation
    When a DC voltage is applied to a capacitor, it is blocked from flowing through the capacitor. This is because a capacitor allows the flow of AC (alternating current) but blocks the flow of DC (direct current). The capacitor acts as an open circuit for DC voltage, preventing it from passing through. Therefore, the correct answer is "It is blocked."

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  • 12. 

    Commercial power is always given in ?

    • Peak to Peak

    • Peak

    • Average

    • RMS

    • Periodic

    Correct Answer
    A. RMS
    Explanation
    Commercial power is always given in RMS (Root Mean Square) because RMS represents the effective value of an alternating current or voltage. In the case of commercial power, which is typically an AC (alternating current) signal, the RMS value is used to calculate the average power delivered to a load. RMS takes into account both the magnitude and the fluctuation of the signal, providing a more accurate measure of power compared to other options like peak, peak to peak, average, or periodic values.

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  • 13. 

    What is the frequency of a waveform that repeats 10 times in a half second ?

    • 10 Hz

    • 20 Hz

    • 500 hz

    • .5 Hz

    • .1 Hz

    Correct Answer
    A. 20 Hz
    Explanation
    The frequency of a waveform is the number of times it repeats per unit of time. In this case, the waveform repeats 10 times in a half second. To find the frequency, we divide the number of repetitions (10) by the time period (0.5 seconds). Therefore, the frequency is 10/0.5 = 20 Hz. Therefore, the correct answer is 20 Hz.

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  • 14. 

    Capacitors in series are the same as ?

    • Inductors in parallel

    • Resistors in series

    • Total impedance

    • Reactance

    • Capacitance reactance

    Correct Answer
    A. Inductors in parallel
    Explanation
    When capacitors are connected in series, their total capacitance decreases. This is similar to when inductors are connected in parallel, where their total inductance decreases. Therefore, the correct answer is "Inductors in parallel".

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  • 15. 

    The power factor is relationship between what to figures ?

    • Average and true power

    • Reactance and average power

    • True and apparent power

    • Apparent and reactance power

    • Resistance and reactance

    Correct Answer
    A. True and apparent power
    Explanation
    The power factor is a measure of how effectively electrical power is being used. It is the ratio of true power (the power actually consumed by the load) to apparent power (the total power supplied to the load). A high power factor indicates efficient utilization of power, while a low power factor indicates wastage of power. Therefore, the relationship between true power and apparent power is important in determining the power factor.

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  • 16. 

    A transformer 400 turns on the primary and 100 turns on the secondary ?

    • Step up 4:1

    • Step up 1:4

    • Step down 1:4

    • Step down 4:1

    • Step up 1:5

    Correct Answer
    A. Step down 4:1
    Explanation
    The given answer, "Step down 4:1," suggests that the transformer is designed to decrease the voltage. This means that the voltage on the primary side is four times higher than the voltage on the secondary side. This step-down ratio indicates that the transformer is intended to reduce the voltage and increase the current, making it suitable for applications where a lower voltage is required.

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  • 17. 

    What is the formula for inductive reactance ?

    • XL = f x L

    • XL = 6.28 x f x t

    • XL = 1 / 6.28 x f x l

    • XL = 6.28 x f x l

    • XL = Square root (XL squared + X squared)

    Correct Answer
    A. XL = 6.28 x f x l
    Explanation
    The formula for inductive reactance is XL = 6.28 x f x l. This formula calculates the inductive reactance (XL) by multiplying the frequency (f) with 6.28 (which is approximately equal to 2π) and the inductance (l). The inductive reactance represents the opposition to the flow of alternating current in an inductor, and it increases with the increase in frequency and inductance.

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  • 18. 

    The portion of the apparent power caused by inductors and capacitors ?

    • Average power

    • Apparent power

    • Reactive power

    • True power

    • The power factor

    Correct Answer
    A. Reactive power
    Explanation
    Reactive power refers to the portion of apparent power that is caused by inductors and capacitors in an electrical circuit. Unlike true power, which represents the actual power consumed by the circuit, reactive power does not perform any useful work. Instead, it oscillates between the source and the reactive elements, creating magnetic and electric fields. Reactive power is measured in volt-amperes reactive (VAR) and is necessary for the proper functioning of electrical systems, but it does not contribute to the overall power consumption or energy usage.

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  • 19. 

    In a transformer how is the frequency when crossing the coils ?

    • Change in magnitude

    • Increases

    • Decreases

    • Stays the same

    • Reduces in magnitude

    Correct Answer
    A. Stays the same
    Explanation
    The frequency stays the same when crossing the coils in a transformer because the primary and secondary coils are connected magnetically, not electrically. The coils are wound around a common core, and the alternating current passing through the primary coil induces a magnetic field in the core. This magnetic field then induces a current in the secondary coil, resulting in the same frequency as the primary coil. Therefore, the frequency remains constant throughout the transformer.

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  • 20. 

    Which of the following best describes resonance in an RLC circuit?

    • Total impedance

    • Increase in capacitive reactance

    • Increase in inductive reactance

    • Impedance is equal to resistance

    • Inductive reactance is equal to capacitive reactance

    Correct Answer
    A. Inductive reactance is equal to capacitive reactance
    Explanation
    Resonance in an RLC circuit occurs when the inductive reactance (XL) is equal to the capacitive reactance (XC). At this point, these two reactances cancel each other out, resulting in the circuit having minimal impedance, which is purely resistive (Z = R). This condition leads to maximum current flow at the resonant frequency.

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  • 21. 

    Total inductive reactance of a 25 henry inductor in a 60 Hz circuit ?

    • 2132 ohms

    • 1.06 ohms

    • 5652 ohms

    • 9420 ohms

    • 6536 ohms

    Correct Answer
    A. 9420 ohms
    Explanation
    The total inductive reactance of an inductor in a circuit is given by the formula Xl = 2πfL, where Xl is the inductive reactance, f is the frequency, and L is the inductance. In this case, the inductance is given as 25 henries and the frequency is 60 Hz. Plugging these values into the formula, we get Xl = 2π(60)(25) = 9420 ohms. Therefore, the correct answer is 9420 ohms.

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  • 22. 

    In a capacitive circuit the charge and discharge current must ?

    • Be simultaneous

    • Be in one direction

    • Always be in different directions

    • Always be out of phase

    • Be in phase

    Correct Answer
    A. Always be in different directions
    Explanation
    In a capacitive circuit, the charge and discharge current must always be in different directions. This is because when the capacitor is charging, the current flows in one direction, and when it is discharging, the current flows in the opposite direction. This alternating flow of current is essential for the functioning of the capacitor and the circuit as a whole.

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  • 23. 

    In an inductive circuit what happens when frequency increases ?

    • No change

    • There is a reduction in inductance

    • There is an increase in inductance

    • There is an increase in inductive reactance

    • There is a decrease in inductive reactance

    Correct Answer
    A. There is an increase in inductive reactance
    Explanation
    When the frequency increases in an inductive circuit, there is an increase in inductive reactance. Inductive reactance is the opposition to the flow of alternating current caused by the inductor in the circuit. As the frequency increases, the inductive reactance also increases, limiting the flow of current through the circuit. This is because the rate of change of current in the inductor becomes greater, resulting in a larger opposition to the current flow.

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  • 24. 

    How is a current transformer connected ?

    • In series

    • In parallel

    • In proximity

    • Across the differing phases

    • Wrapped

    Correct Answer
    A. In series
    Explanation
    A current transformer is connected in series with the circuit that carries the current to be measured. By connecting it in series, the current flowing through the transformer is proportional to the current flowing through the circuit. This allows the current transformer to accurately measure and transform high currents to lower, more manageable levels for measurement or protection purposes. Connecting it in parallel or across differing phases would not provide an accurate measurement of the current, while wrapping it around the circuit is not a proper method of connection.

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  • 25. 

    At resonance what happens to resistance ?

    • Nothing

    • It decrease

    • Capacitance cancels out resistance

    • It increases

    • All the above

    Correct Answer
    A. Nothing
    Explanation
    At resonance, the resistance in a circuit remains unchanged. This is because resonance occurs when the inductive reactance and the capacitive reactance cancel each other out, resulting in a purely resistive circuit. Therefore, the resistance does not increase or decrease but stays the same.

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  • 26. 

    RMS power is ?

    • Average power

    • True power

    • Apparent power

    • Distributed power

    • Peak to Peak power

    Correct Answer
    A. True power
    Explanation
    True power refers to the actual power consumed or delivered by an electrical device. It is the power that is converted into useful work or dissipated as heat. True power takes into account both the resistive and reactive components of the load, providing an accurate measure of the power being used. This is different from apparent power, which only considers the magnitude of the power and does not take into account the phase difference between the voltage and current. RMS power, on the other hand, is the root mean square value of the power waveform and is a measure of the average power over time. Therefore, the correct answer for the given question is true power.

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  • 27. 

    What is the period of a waveform with a frequency of 60hz ?

    • 17 milliseconds

    • 1.7 milliseconds

    • 170 milliseconds

    • .17 seconds

    • 1.7 seconds

    Correct Answer
    A. 17 milliseconds
    Explanation
    The period of a waveform is the time it takes for one complete cycle. The frequency is the number of cycles per second. To find the period, we can take the reciprocal of the frequency. In this case, the frequency is 60Hz, so the period is 1/60 seconds. Converting this to milliseconds, we get 1000/60 milliseconds, which is approximately 16.67 milliseconds. Since none of the given options match exactly, the closest answer is 17 milliseconds.

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  • 28. 

    The power consumed by resistance is ?

    • Average power

    • Apparent power

    • Reactive power

    • True power

    • The power factor

    Correct Answer
    A. True power
    Explanation
    The correct answer is "True power." True power refers to the actual power consumed by a resistance in a circuit. It is the power that is converted into useful work or dissipated as heat. True power is measured in watts and is calculated by multiplying the voltage across the resistance by the current flowing through it. This is different from reactive power, which represents the power that oscillates between the source and the load due to the presence of inductance and capacitance in the circuit.

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  • 29. 

    What is the total capacitance when two 40 microfarad capacitors are connected in parallel?

    • 10 μF

    • 40 μF

    • 80 μF

    • 20 μF

    • 5 μF

    Correct Answer
    A. 80 μF
    Explanation
    When capacitors are connected in parallel, the total capacitance is the sum of the individual capacitances. Therefore, two 40 microfarad capacitors connected in parallel result in a total capacitance of 80 microfarads (40 μF + 40 μF = 80 μF).

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  • 30. 

    What is the peek voltage of a 120Vac circuit ?

    • 117 volts

    • 120 volts

    • 150 volts

    • 170 volts

    • 110 volts

    Correct Answer
    A. 170 volts
  • 31. 

    Total opposition of current flow in a circuit ?

    • Capacitance reactance

    • Impedance

    • Inductive reactance

    • Resistance

    • Resistive reactance

    Correct Answer
    A. Impedance
    Explanation
    Impedance refers to the total opposition of current flow in a circuit. It is a combination of resistance, which is the opposition to the flow of current in a circuit, and reactance, which is the opposition to the change in current flow caused by inductors or capacitors. Therefore, impedance encompasses both resistive and reactive components and represents the overall opposition to current flow in a circuit.

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  • 32. 

    The product of the source voltage and total current ?

    • Average power

    • Apparent power

    • Reactive power

    • True power

    • The power factor

    Correct Answer
    A. Apparent power
    Explanation
    Apparent power is the product of the source voltage and total current. It represents the total power that is being supplied to a circuit, including both the real power (which is used to perform useful work) and the reactive power (which is used to establish and maintain the electric and magnetic fields in the circuit). Apparent power is measured in volt-amperes (VA) and is important for sizing electrical equipment and determining the capacity of electrical systems.

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  • 33. 

    On a current transformer which set of windings always has more turns ?

    • They are the same

    • The primary

    • The like-wound side

    • The secondary

    • The unlike-wound side

    Correct Answer
    A. The secondary
    Explanation
    The secondary winding of a current transformer always has more turns compared to the primary winding. This is because the primary winding is responsible for carrying the actual current, while the secondary winding is used to measure or monitor the current. In order to step down the current to a manageable level for measurement, the secondary winding needs to have more turns.

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  • 34. 

    True power is the product of resistance and ?

    • Voltage

    • Current squared

    • Reactance

    • Current

    • Voltage squared

    Correct Answer
    A. Current squared
    Explanation
    The correct answer is "Current squared." In electrical circuits, true power is calculated by multiplying the resistance of the circuit by the square of the current flowing through it. This is known as the formula for power, P = I^2 * R, where P represents power, I represents current, and R represents resistance. Therefore, the product of resistance and current squared gives the true power in a circuit.

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  • 35. 

    A transformer in which the primary and secondary voltages are out of phase ?

    • Current transformer

    • Autotransformer

    • Like-wound

    • Dotted

    • Unlike-wound

    Correct Answer
    A. Unlike-wound
    Explanation
    An unlike-wound transformer is a type of transformer where the primary and secondary windings are wound in opposite directions. This results in a phase shift between the primary and secondary voltages. When the primary voltage is at its maximum, the secondary voltage will be at its minimum, and vice versa. This phase shift can be useful in certain applications where a specific phase relationship between the primary and secondary voltages is required.

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  • 36. 

    Unlike a resistor, which of the following components has no power dissipation in an ideal case?

    • Inductor

    • Circuit

    • Capacitor

    • Capacitance circuit

    • Dielectric

    Correct Answer
    A. Capacitor
    Explanation
    In an ideal capacitor, there is no power dissipation because it stores energy in the form of an electric field and releases it without any loss. Unlike resistors, which convert electrical energy into heat, ideal capacitors and inductors do not dissipate power. They merely store and release energy periodically.

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  • 37. 

    A Henry is a measurement of what ?

    • Resitance

    • Capacitance

    • Reactance

    • Impedance

    Correct Answer
    A. Impedance
    Explanation
    A Henry is a measurement of impedance. Impedance refers to the total opposition to the flow of alternating current in a circuit, including both resistance and reactance. It is measured in ohms and is represented by the symbol Z. The unit Henry is specifically used to measure inductance, which is a type of reactance caused by the presence of an inductor in a circuit. Therefore, the correct answer is impedance.

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  • 38. 

    Which characteristic of an electrical circuit opposes the change in current flow?

    • Resistance

    • Capacitance

    • Inductance

    • Impedance

    • Reactance

    Correct Answer
    A. Inductance
    Explanation
    Inductance is the property of an electrical circuit that opposes changes in current flow. It does so by generating a voltage (known as back EMF) that opposes the change in current. This characteristic is fundamental in inductors, which resist changes in current by temporarily storing energy in a magnetic field.

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  • 39. 

    What is the formula to find the average voltage ?

    • Average = .707 x Peak

    • Average = RMS / .707

    • Average = .673 x Peak

    • Average = Peak x .637

    • Average = Peak x .077

    Correct Answer
    A. Average = Peak x .637
    Explanation
    The formula to find the average voltage is given by Average = Peak x .637. This formula suggests that to calculate the average voltage, you need to multiply the peak voltage value by 0.637.

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  • 40. 

    What is the wavelength of a waveform ?(Multiple)

    • The times per second a waveform repeats

    • Time for a waveform to complete one cycle

    • Used to average a waveform

    • The distance traveled by a waveform during one second

    • The Lambda of a waveform

    Correct Answer(s)
    A. The distance traveled by a waveform during one second
    A. The Lambda of a waveform
    Explanation
    The wavelength of a waveform refers to the distance traveled by the waveform during one second. It represents the spatial length of one complete cycle of the waveform. The term "Lambda" is often used to symbolize the wavelength of a waveform.

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  • Sep 24, 2024
    Quiz Edited by
    ProProfs Editorial Team
  • Dec 08, 2009
    Quiz Created by
    Jbreshears
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