36 Questions
What is the average value of the voltage values occurring during a complete cycle of a sinusoidal waveform?
Zero
What type of multimeter measurement values are most commonly displayed?
RMS values
What is the unit of measurement for electrical phase?
Degrees
What is the condition when the voltage and current sine waves cross the zero line at the same time?
In phase
What is the purpose of a True Value RMS meter?
To measure RMS values accurately
What is the result when more than one AC power source is perfectly paralleled together?
They are in phase
What determines the direction of current movement in an AC generator?
The generated terminal voltage polarities
What is the characteristic of the amplitude of the positive and negative alternations in an AC waveform?
The amplitude of the positive alternation and the amplitude of the negative alternation are the same
What is the representation of induced EMF for a single coil rotated through a uniform magnetic field at a constant speed?
A sinusoidal sine wave
What is the main difference between AC and DC currents?
AC flows in one direction and then in the opposite direction, while DC flows in one direction only
What is the relationship between the speed of the conductor cutting lines of flux and the potential difference?
A faster conductor cutting lines of flux produces a greater potential difference
What is the most common AC waveform?
Sine (or sinusoidal) waveform
What is the RMS value of a sine wave in relation to its peak value?
0.707 times the peak value
How is the average value of an alternating current or voltage calculated?
By adding together a series of instantaneous values and dividing by the number of values
What is the symbol used to represent the RMS value?
VRMS or IRMS
What is the average value of one alternation of a sine wave in relation to its peak value?
0.637 times the peak value
What do voltmeters typically measure?
Average value
What is the definition of Root Mean Square (RMS) value according to most books?
The amount of AC power that produces the same heating effect as an equivalent DC power
What is the definition of an alternation in an AC cycle?
Half of an AC cycle, where the voltage or current rises or falls from zero to a peak and back to zero
What is the unit of measurement for the frequency of AC?
Hertz (Hz)
What is the period of a waveform if the frequency is 400 Hz?
0.0025 s
What happens to the frequency of AC if the number of revolutions of the coil per second is increased?
It increases
What is the relationship between the frequency and period of a waveform?
The frequency is inversely proportional to the period
What is the time required to complete one cycle of a waveform?
Period
What does the vertical axis of a sine wave represent?
Magnitude and direction of current or voltage
What happens when the waveform is below the time axis?
Current is said to be flowing in a negative direction
What determines the amplitude of an AC waveform?
The speed of the conductor cutting lines of flux
What is the characteristic of an AC waveform?
Flows first in one direction and then in the opposite direction
What is the relationship between the speed of the conductor cutting lines of flux and the potential difference?
The faster the speed, the greater the potential difference
What is the result of a complete cycle of a sine wave?
Two identically shaped variations in voltage
What is the duration of flow in one direction of an alternating current?
A half-period
What determines the frequency of a sinusoidal waveform?
The number of cycles per second
What is the characteristic of a three-phase AC power system?
Three AC power sources that are out of phase with each other
What is the term for the duration of all half-periods in a sinusoidal waveform?
Period
What is the relationship between the frequency and period of a sinusoidal waveform?
Frequency is inversely proportional to period
What is the characteristic of the AC cycle in a sinusoidal waveform?
The voltage and current sine waves cross the zero line at the same time
Understanding AC sine wave measurements, including peak-to-peak values and RMS values, and how multimeters display these values. This is crucial for aircraft maintenance and repair.
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