WorksheetsA.C. Circuits Study Guide
Total questions: 99
Worksheet time: 25hrs 45mins
What is the instantaneous voltage at 42 degrees on a 230Vp sine wave?
115V
154V
76.1V
149V
Which one of the following represents the value at point G in figure 8-1
the peak voltage
the RMS voltage
the frequency
the period
The square wave is made up of:
The fundamental frequency and all the even harmonics.
The fundamental frequency and all the odd harmonics.
Just the fundamental frequency.
The fundamental frequency and both the odd and even harmonics.
Troubleshooting an AC circuit can be performed with which of the following tools?
Oscilloscope
Digital Multimeter
Analog voltmeter
All of the above
Superimposed DC and AC voltages mean the two voltages are combined:
in series-parallel aiding or opposing.
in parallel aiding or opposing.
in series aiding or opposing.
All of these
Which point in figure 8-1 is 180 degrees away from point E?
A
B
C
D
If R1 shorts in Figure 8-2, VR2...
increases
remains the same
decreases
Calculate current total in figure 8-2.
6.44mApp
9.12mApp
4.55mApp
3.22mApp
If a 10 K Ohm resistor carries 5 mARMS of current, its voltage drop equals...
7.07 VRMS
50 VRMS
70.7 VRMS
5 VRMS
The time required by a 10V square wave to change from 1V to 9V is known as the...
fall time
pulse width
period
rise time
What is the instantaneous voltage at 284 degrees on a 22Vpp sine wave?
-2.66V
0.33V
10.7V
-10.7V
In figure 8-1, if the time from point A to H is 60 microseconds, the frequency is...
16.7 kHz
50 kHz
25 kHz
More information is required to calculate the frequency.
What is the approximate peak input voltage to the circuit in Figure 8-2?
28.3 Vp
10 Vp
20 Vp
14.1 Vp
7.07 Vpp is approximately equal to 2.5 VRMS
True
False
Kirchhoff's voltage law can be used with resistive ac circuits.
True
False
An ac current is inversely proportional to an ac voltage.
True
False
The term RMS means "Root Mean Square".
True
False
A sine Wave's frequency equals the reciprocal of its period.
True
False
In a two resistor series circuit VR1 = 6.5 VRMS and VR2 = 3.2 VRMS. The source voltage is...
9.19 Vp
13.7 Vp
9.7 Vp
4.53 Vp
The symbol from the period of a wave form is...
W
F
P
T
How much voltage is dropped across a 150 microfarad capacitor after 3.33 seconds if it is charged by a 50 V source through a 22K Ohm resistor?
47.5 V
43.3 V
49 V
31.8 V
At What frequency is a 0.001 microfarad capacitor operating if its reactance is 45K Ohms?
3.54 kHz
3.54 MHz
354 kHz
35.4 kHz
Electrolytic capacitors differ from many other capacitors in construction in that they are:
smaller
larger
sensitized
polarized
A commonplace use for capacitors in electronics is to:
block DC voltages
pass both AC and DC voltages
block AC voltages
pass DC voltages only
With three capacitors in series, the current lags the voltage by:
30 degrees
45 degrees
90 degrees
none of the above
What is one time constant of a 4.7 microfarad capacitor in series with a 22k Ohm resistor?
103 ms
0.103 ms
10.3 ms
1.03 ms
If a 1 microfarad capacitor and a 10k Ohm resistor are connected in series across 20V DC, approximately how much voltage will the capacitor drop after charging for just one time constant?
12.6 V
11 V
17 V
12.1 V
If a 22 microfarad is connected to a 15 V 400 Hz source, its current equals...
1.81 A
829 mA
55 mA
18.1 mA
if a 0.05 microfarad and 0.1 microfarad capacitor are connected in parallel across a 20 V source, the total capacitance equals... and each capacitor drops...
0.05 microfarads and 15 V
0.15 microfarads and 20 V
0.10 microfarads and 20 V
0.15 microfarads and 10 V
How long will it take a 0.047 microfarad capacitor to fully charge through a 100k Ohm resistor?
235 ms
0.235 ms
23.5 ms
2.35 s
When capacitors are connected in series, their total capacitance act like:
resistance connected in series
resistance connected in series-parallel
resistance connected in parallel
All of these
What is the small amount of power lost in a capacitive circuit due to the internal resistance of the capacitors?
reactive power
instantaneous power
ideal power
true power
In a capacitive AC circuit, the phase relationship between the voltage and the current is such that the:
current is leading the voltage
voltage is 360 degrees out phase with current
voltage is leading the current
current is 180 degrees out of phase with voltage
In a capacitive AC circuit, the phase relationship between the voltage and the current is such that:
current is leading the voltage
voltage is 360 degrees out of phase with current
voltage is leading the current
Current is 180 degrees out of phase with voltage
The time constant of a capacitor is
all of these
directly proportional to the capacitive in the circuit
directly proportional to the resistance in the circuit
the time required to charge to 63% or discharge to 37%
if the dc working voltage of a capacitor is 100 V, the dielectric must withstand
220 Vpp
85 Vpp
100 Vpp
75 Vrms
when two capacitors are connected in parallel across a dc source, the smaller capacitor drops the larger voltage
True
False
A capacitor blocks DC passes AC
True
False
capacitance is the ability to store voltage
True
False
If the operating frequency increases in Figure 10-1, How does the resistor value change?
it decreases
It increases
it remains the same
it opens
If the frequency increases in Figure 10-1, the phase angle _____ and the impedance______
Decreases, Increses
Increases, Increases
Decreases, Decreases
Increases, Decreases
If the output were taken across the resistor in Figure 10-3, the circuit would be known as a_____
Low-pass filter
band-pass filter
high-pass filter
band-notch filter
If the operating frequency decreases in Figure 10-1, how does the capacitance value change?
It decreases
It decreases to zero
it increases
it remains the same
Which statement describes the relationship of Ic and Ir, in Figure 10-2
Ic leads Ir
They are 180 degrees out of phase
They are in phase
Ic lags Ir
What is the true power in Figure 10-1
5.73 W
916 mW
275 mW
5.73 mW
If the frequency equals 60 Hz Figure 10-1, what is the value of capacitance
22 uF
44 uF
88 uF
66 uF
An RC lag network is similar to a
High pass filter
Band pass filter
low pass filter
stop pass filter
What change would increase the power factor in Figure 10-2
decreasing the value of the capacitor
increasing the value of the capacitor
increasing the value of the resistor
increasing the value of the source value
How much voltage does the resistor drop in figure 10-2
10 V
19.94 V
20 V
59 mV
As the frequency applied to an RC circuit varies, both Xc and resistance vary
True
False
As the frequency applied to an RC circuit increases, the impedance decreases
True
False
when the frequency applied to an RC circuit varies, the value of Xc varies
True
False
The total current in an RC circuit always leads the source voltage
True
False
Power factor values close to 0 denotes an RC circuit with mostly true power
True
False
What is the circuit's impedance in Figure 10-1?
520 Ω
120 Ω
418 Ω
280 Ω
The phasor combination of Vr and Vc in an RC series circuit equals the source voltage
True
False
If the true power is 100 W and the reactive power is 100 VAR, The apparent power is______
200 VA
141 VA
141 W
100 VA
What is the circuit fault in Figure 10-3 if the output voltage equals 0 V at the cutoff frequency
The capacitor has shorted
The capacitor has opened
The capacitor has become leaky
The resistor has shorted
If the resistor value increases in Figure 10-2, then how does the total current change
it decreases to zero
it remains the same
it decreases
it increases
if two inductors are connected in a series AC circuit which inductor drops more voltage?
The larger inductance
The smaller inductance
It depends upon the source voltage
It depends upon the frequency
What is the reactance of a 100 uH inductor operating at 100 KHz
6.28 Ω
62.8 Ω
62.8 KΩ
Infinite Ω
the time constant of an inductor is
the time required for voltage of current to increase to 63% to decrease to 37%
inversely proportional to the resistance in the circuit
directly proportional to the inductance in the circuit
all of these
What is the total inductance if a 50 mH inductor is connected in series with a 15 mH inductor
65 mH
11.5 mH
50 mH
15 mH
What is the inductance of a 20 mH inductor connected in parallel with a 50 mH
50 mH
70 mH
20 mH
14.3 mH
Inductors ____
block direct current
have high reactance to direct current
have a high resistance to direct current
pass direct current
Connecting a _____ inductor in _____ with a 70 mH inductor produces a 100 mH inductance
30 mH, series
30 mH, parallel
233 mH, series
233 mH, parallel
if a 25 mH inductor drops 50V while operating at 400 Hz, what is XL
628Ω
6.28 Ω
62.8 Ω
62.8 kΩ
connecting a _____ inductor in ____ with a 100 mH inductor produces 65 mH inductance
186 mH, Parallel
186 mH, series
35 mH, parallel
35 mH, series
the quality factor of a coil or inductor is calculated by
Ql = 2*Pi*f*L
Ql = 1/(2*Pi*F*L)
Ql = L/R
Ql = 2*Pi*F*L/Rw
In an inductive AC circuit, the phase relationship between the voltage and the current is such that the:
Current is 180 degrees out of phase with voltage
Voltage is lagging the current
Voltage is 360 degrees out of phase with voltage
current is lagging the voltage
What is the inductive reactance of a 150 mH inductor operating at 10 KHz
8450 Ω
6280 Ω
9420 Ω
1500 Ω
The energy stored in an inductor's electromagnetic field is produced by the resistance of the inductor's winding
true
false
An inductor passes direct current and opposes alternating current
true
false
Inductive reactance decreases as frequency increases
true
false
inductors in series or parallel combine just like resistors in series or parallel
true
false
the total inductance of two parallel inductors equals the sum of their inductance values
true
false
if an inductor is placed in an AC circuit, the AC voltage across the inductor leads the AC current through it
True
false
True power for an inductor is measured in VAR rather than watts
True
False
if two 2.5 mH inductors are connected in series with a 4.7 kΩ resistor and the source voltage is 100 Vdc, what is the circuit's maximum current?
21.3 mA
1.1 mA
7.9 mA
63.2 mA
If true power is 10 W and the reactive power is 10 VAR, the apparent power is...
14.1 VA
20 VA
100 VA
5 VAT
If the resistive current is 2 A and the inductive current is 2 A in a parallel RL circuit, total current is...
5.66 A
2 A
4 A
2.83 A
If a low pass filter's cutoff frequency is 20kHz, its bandwidth is...
0 Hz
40 Hz
20 Hz
unknown
When an ac voltage is supplied to an RL circuit, the ac's current and amplitude will be:
similar in waveform
varying in the same manner
lagging the voltage
all of these
An RL high pass filter takes its output across:
the series inductor
the series resistor
the parallel resistor
the parallel inductor
What is the cutoff frequency in figure 12-3?
637 kHz
637 Hz
7.96 kHz
796 Hz
If the output is taken across the inductor in Figure 12-3, the circuit is known as...
high-pass filter
notch filter
band-pass filter
low-pass filter
If a load is purely inductive and the reactive power is 10 VAR, the apparent power is...
3.16 VA
10 VA
14.14 VA
1.144 VA
If the frequency increases in figure 12-1, the phase angle... and the current..
decreases, decreases
increases, decreases
increases, increases
increases, decreases
What effect will an open inductor have on the circuit in Figure 12-3?
The current will drop to zero.
The cutoff frequency will increase.
The output voltage at the cutoff frequency will increase.
The output voltage at the cutoff frequency will decrease.
What is the phase angle in figure 12-3, at the cutoff frequency?
54.3 degrees
51.4 degrees
49.5 degrees
45.0 degrees
A measured voltage of 0 V across the resistor in a parallel RL circuit would indicate:
a blown fuse
an open in the resistor
a short in the inductor
either A or B
Calculate true power in figure 12-1.
4 W
1 W
400 mW
10 W
What change would decrease the power factor in figure 12-2?
Decrease the source voltage.
Increase the value of the resistor.
Increase the source voltage.
Decrease the value of the resistor.
A low-pass filter passes high frequencies and blocks other frequencies.
True
False
The source voltage always leads the total current in an RL circuit.
True
False
The output at the cutoff frequency of a low pass RL filter is 0 V.
True
False
In the frequency increases in an RL circuit, the impedance decreases.
True
False
A high-pass filter passes high frequencies and blocks low frequencies.
True
False
What is the impedance in figure 12-1?
1040 Ohms
112 Ohms
1120 Ohms
104 Ohms
