AC Flashcards
Which section of an oscilloscope controls amplitude?
Vertical Control Section
Which section of an oscilloscope controls sweep?
The Horizontal Controls
Which control on an oscilloscope controls the brightness of the trace?
Intensity Control
Where can the graticule (grid) be found on an oscilloscope?
Display Section
What is the easiest voltage amplitude to measure by viewing a pure sine wave signal on an oscilloscope?
Peak to Peak
Which section of an oscilloscope helps stabilize the displayed waveform for a technician to make accurate measurements?
Trigger Section
Which electronic diagnostic test instrument displays waveforms in the Time-Domain?
Oscilloscope
Which electronic diagnostic test instrument displays waveforms in the Frequency-Domain?
Spectrum Analyzer
Which diagnostic test instrument generates different waveforms at varying amplitudes and frequency for the purpose of injecting signals into electronic circuits under test?
Function Generator
When induced currents produce expanding magnetic fields around conductors in a direction that opposes the original magnetic field, this is known as:
Lenz’s Law
When using the left hand rule for coils, what do the wrapped fingers represent?
Current flow direction
When using the left hand rule for conductors, what does the thumb represent?
Electron Current Flow Direction
What formula would calculate the total inductance of inductors in series?
Lt = L1 + L2
What is the term for the time required for the current in an RL circuit to build up to 63.2% of the maximum value?
One Time Constant
Given a circuit with an inductor of 100 microH in series with a capacitor of .001nF, operating at a frequency of
10 MHz. What is the net reactance?
9.63 kOhms - capacitive
What is the reactance of two parallel inductors L1=10 mH, and L2= 5mH at a frequency of 100 Hz?
2.09 Ohms
In an AC circuit where the voltage and current are out of phase, how can the true power be determined?
By multiplying the apparent power with the power factor
What is the power factor of a circuit with a true power of 5.10 watts and an apparent power of 9.85 volt amps?
0.52
What happens to reactive power in a circuit that has both inductors and capacitors?
Is returned to the source and is not dissipated
What leads in a capacitive circuit?
Current leads voltage
Capacitive reactance will increase with a/an:
Decrease in capacitance and or frequency
What factors determine the capacitance of a capacitor?
Distance between the plates and the dielectric constant of the material between the plates
The opposition to a change in AC voltage offered by a capacitor is known as:
Capacitive Reactance
One “time constant” of an RC circuit is the time required to charge the capacitor in the circuit to what percentage of maximum capacity?
63.2% of the supply voltage
What does a Coupling Capacitor do?
Blocks DC and passes AC
What does a bypass Capacitor do?
Shunts AC to ground
After two time constants, the capacitor in an RC circuit is discharged to what percentage of the starting voltage?
13.5%
What is the capacitive reactance of a 0.1 mf capacitor and a 0.4 m capacitor in series operating with a source voltage of 120V and a frequency of 10 Hz?
199.0 Ohms
What is the capacitive reactance (Xc) of two parallel capacitors C1=10 microF, and C2= 5 microF at a frequency of 100 Hz?
106.1 Ohms
A capacitors voltage should be selected so it is at least _______ greater than the highest applied voltage?
50%
What is the approximate magnitude of the impedance of a series R-L-C circuit at resonance?
Approximately equal to circuit resistance
What is the magnitude of the impedance of a series AC circuit having a resistance of 10 ohms, an inductive reactance of 20 ohms, and zero capacitive reactance?
22.36 Ohms
What is the impedance of a circuit containing a 1K OHMS resistor, a 2mh inductor and a 12.678 microF capacitor in series operating at a frequency of 1Khz?
1 kOhms
What does a “Phasor” indicate?
Direction/Angle and Magnitude/Quantity
The angular measurement of a Sine wave can be expressed or plotted in what two (2) forms?
Polar & Cartesian
What theorem is used to find the Hypotenuse of a right triangle?
Pythagorean Theorem
What is meant by an aircraft having polyphase power?
Aircraft has 3 phase power
The two configurations of three phase (polyphase) AC power are?
Delta and Wye
What is the phase difference between 3 phases of AC?
120 degrees
Two coils are arranged so that all of the flux lines of one coil cut all of the turns of the other coil. The ratio between these is known as what?
Coefficient of Coupling
What does a coefficient of coupling of 0 indicate?
No lines of flux cut the secondary windings
A step-up transformer steps up what?
Voltage
Transformers with the secondary voltage in phase with the primary are known as what type of transformer?
Like-wound transformer
What is the efficiency of a power transformer that has an output power of 950 W and input power of 1010 W?
94.1%
What is the secondary current of a 20/1 transformer if the primary current is 1.5 amps?
30 amps
What type of power loss occurs when current changes polarity or direction and the alignment of the atoms and the direction of magnetic lines of flux also change polarity?
Hysteresis Loss
What type of power loss is defined as conductive I?R (Power) loss produced by circulating currents induced in response to AC flux linkage flowing around the turns of the coil and against the internal resistance of the core?
Eddy Current Loss
A transformer has a primary of 120 volts, a secondary of 15 volts. A 150-watt buzzer is connected to the secondary. The resistance of the buzzer is
______ ohms.
1.5
If the period of a sine wave is provided, how do you find the frequency?
Use 1/T as the equation to find frequency
What is the basic unit of measurement for frequency?
Hertz
What is the frequency of a circuit whose time for one cycle is 700mS?
1.43 Hz
How degrees is 1 Radian equal to?
57.3
How many Radians is equal to 1 Degree?
0.017
The Cosine of an angle in a right triangle is found by taking the dividend of what two sides of the right triangle?
Adjacent/Hypotenuse
When does the positive peak peak amplitude in a sine wave occur?
90 degrees
If you know the Power Factor (PF) of a series RLC circuit, how do you find the Phase Angle?
Cos-1(PF)
To convert peak to peak voltage to rms voltage?
(Peak to peak divided by 2) x 0.707
What is the peak voltage of 120V RMS voltage at 60 Hz?
169.7 v
What is the Average voltage of 120V RMS voltage at 60 Hz?
108.1 v
