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MECH1310Chapter8Homework

True/False
Indicate whether the statement is true or false.
 

 1. 
A sine wave's frequency equals the reciprocal of its period.
 

 2. 
The higher a sine wave's frequency, the shorter its period.
 

 3. 
A sine wave's peak value is smaller than its RMS value.
 

 4. 
An ac current is inversely proportional to an ac voltage.
 

 5. 
One complete sine wave contains 360°.
 

 6. 
RMS is another name for peak.
 

 7. 
7.07 VPP is approximately equal to 2.5 VRMS.
 

 8. 
The term RMS stands for "root-mean-square."
 

 9. 
The period of a 5 Hz wave form is 200 ms.
 

 10. 
Commercial line voltages are usually square waves at a frequency of 60 Hz.
 

 11. 
Current flows both ways simultaneously in an AC circuit.
 

 12. 
Only frequency increases with the speed of an AC generator.
 

 13. 
20 Vrms of alternating current will illuminate a given lamp at the same intensity as 20 V of direct current.
 

 14. 
Rise time, fall time, and duty cycle are all terms associated with sine wave measurement.
 

 15. 
Kirchhoff's voltage law can be used with resistive ac circuits.
 

Multiple Choice
Identify the choice that best completes the statement or answers the question.
 

 16. 
The RMS value of a sine wave means ________.
a.
the same as IP × R
b.
the same as IPP × R
c.
the root mean square value
d.
the heating effect of an ac generator of the same voltage
 

 17. 
What is the instantaneous voltage at 42° on a 230 VP sine wave?
a.
154 V
c.
149 V
b.
115 V
d.
76.1 V
 

 18. 
Which one of the following represents the value at point G in Figure 8-1?
mc018-1.jpg
Figure 8-1
a.
the frequency
c.
the period
b.
the peak voltage
d.
the RMS voltage
 

 19. 
which of the following can be measured from points B to F in Figure 8-1?
mc019-1.jpg
Figure 8-1
a.
the angle
c.
the frequency
b.
the peak-to-peak voltage
d.
the period
 

 20. 
VPP is measured between points ________ in Figure 8-1.
mc020-1.jpg
Figure 8-1
a.
C and H
c.
G and I
b.
D and F
d.
A and B
 

 21. 
Which point in Figure 8-1 is 180° away from point E?
mc021-1.jpg
Figure 8-1
a.
A
c.
C
b.
B
d.
D
 

 22. 
In Figure 8-1, the time from point C to E is called ________.
mc022-1.jpg
Figure 8-1
a.
a cycle
c.
peak voltage
b.
a half-cycle
d.
the period
 

 23. 
In Figure 8-1, which of the following can be measured from point E to point F?
mc023-1.jpg
Figure 8-1
a.
the RMS voltage
c.
the peak to peak voltage
b.
one cycle of voltage
d.
the peak voltage
 

 24. 
In Figure 8-1, if the time from point A to H is 60 ìs the frequency is ________.
mc024-1.jpg
Figure 8-1
a.
16.7 kHz
b.
25 kHz
c.
50 kHz
d.
More information is required to calculate the frequency.
 

 25. 
Calculate VR2 in Figure 8-2.
mc025-1.jpg
Figure 8-2
a.
4.84 VP
c.
13.15 VP
b.
6.84 VP
d.
6.84 VPP
 

 26. 
What is the approximate peak input voltage to the circuit in Figure 8-2?
mc026-1.jpg
Figure 8-2
a.
10 VP
c.
28.3 VP
b.
14.1 VP
d.
20 VP
 

 27. 
Calculate VR1 in Figure 8-2.
mc027-1.jpg
Figure 8-2
a.
13.2 VP
c.
6.84 VP
b.
13.7 VP
d.
21.4 VP
 

 28. 
In Figure 8-2, what is the instantaneous voltage across R1 at an angle of 22°?
mc028-1.jpg
Figure 8-2
a.
12.0 V
c.
2.56 V
b.
20.3 V
d.
8.03 V
 

 29. 
VR2 ________ if R1 opens in Figure 8-2.
mc029-1.jpg
Figure 8-2
a.
remains the same
c.
decreases
b.
increases
 

 30. 
Find RT in Figure 8-2.
mc030-1.jpg
Figure 8-2
a.
6.2 kÙ
c.
4.7 kÙ
b.
4.77 kÙ
d.
1.13 kÙ
 

 31. 
Find PR1 in Figure 8-2.
mc031-1.jpg
Figure 8-2
a.
97.8 mW
c.
0 W
b.
196 mW
d.
48.9 mW
 

 32. 
If R1 shorts in Figure 8-2, VR2 ________.
mc032-1.jpg
Figure 8-2
a.
increases
c.
decreases
b.
remains the same
 

 33. 
In Figure 8-2, what is the instantaneous voltage across R1 at 122°?
mc033-1.jpg
Figure 8-2
a.
11.2 V
c.
18.2 V
b.
5.8 V
d.
11.6 V
 

 34. 
Calculate IT in Figure 8-2.
mc034-1.jpg
Figure 8-2
a.
4.55 mAPP
c.
3.22 mAPP
b.
9.12 mAPP
d.
6.44 mAPP
 

 35. 
If you measure about 56 VPP across the source in Figure 8-2, what is the trouble?
mc035-1.jpg
Figure 8-2
a.
R2 is open.
b.
Both R1 and R2 are open.
c.
R1 is open.
d.
There is no trouble. 56 VPP is a normal measurement for the source voltage.
e.
any of these
 

 36. 
Calculate the total power dissipation in the circuit in Figure 8-2.
mc036-1.jpg
Figure 8-2
a.
9.12 mW
c.
182 mW
b.
64.5 mW
d.
45.6 mW
 

 37. 
In Figure 8-2, if you look at VR1 with an oscilloscope and you find no trace, a possible trouble might be that ________.
mc037-1.jpg
Figure 8-2
a.
R2 is shorted
c.
R1 is open
b.
R2 is open
d.
the resistance of R2 has changed
 

 38. 
What is the instantaneous voltage at 284° on a 22 VPP sine wave?
a.
-2.66 V
c.
0.33 V
b.
10.7 V
d.
-10.7 V
 

 39. 
If a rectangular wave's pulse width is 50 ìS and its frequency is 4 kHz, its duty cycle is ________.
a.
98.75%
c.
80%
b.
20%
d.
1.25%
 

 40. 
The time required by a 10 V square wave to change from 1 V to 9 V is known as the ________.
a.
rise time
c.
fall time
b.
pulse width
d.
period
 

 41. 
What is the approximate instantaneous voltage at 37° on a 169 VP sine wave?
a.
239 V
c.
102 V
b.
135 V
d.
119 V
 

 42. 
A 60 Hz sine wave completes ________ cycles every 10 seconds.
a.
10
c.
600
b.
1/16
d.
6
 

 43. 
A 10 VP sine wave is equal to ________.
a.
100 VPP
c.
20 VPP
b.
5 VPP
d.
none of the above
 

 44. 
A sine wave's instantaneous voltage is 0 V at ________ degrees.
a.
360
c.
180
b.
0
d.
all of these
 

 45. 
If a 10 kÙ resistor carries 5 mARMS of current, its voltage drop equals ________.
a.
70.7 VRMS
c.
50 VRMS
b.
5 VRMS
d.
7.07 VRMS
 

 46. 
In a two-resistor series circuit VR1 = 6.5 VRMS and VR2 = 3.2 VRMS. The source voltage is ________.
a.
4.53 VP
c.
13.7 VP
b.
9.19 VP
d.
9.7 VP
 

 47. 
A formula for VRMS is ________.
a.
0.707 × VP
c.
2.8 × VP
b.
2 × VP
d.
0.707 × VPP
 

 48. 
What is the instantaneous voltage at 17° on a 169 VP sine wave?
a.
98.8 V
c.
80.5 V
b.
161 V
d.
49.4 V
 

 49. 
A 12 VP sine wave equals ________.
a.
7.64 VAVG
c.
24 VPP
b.
8.48 VRMS
d.
all of these
 

 50. 
An oscilloscope's volts/division switch is set on 50 mV/div. If the vertical deflection of the oscilloscope's trace is 1.6 division, what voltage is being measured?
a.
80 mV
c.
0.008 V
b.
1.6 mV
d.
50 mV
 

 51. 
An oscilloscope's seconds/division switch is set on 20 ms/div. If a sine wave measures 4 divisions horizontally, what frequency is being measured?
a.
25 Hz
c.
50 Hz
b.
12.5 Hz
d.
More information is needed.
 

 52. 
An oscilloscope's seconds/division switch is set on 20 ìs/cm. If the trace is 7.5 cm long, what is the period?
a.
0.0015 s
c.
1.5 ìs
b.
150 ìs
d.
5 ìs
 

 53. 
If the period of a square wave is 22 ms, what is its frequency?
a.
45.5 kHz
c.
45.5 Hz
b.
22 kHz
d.
22 Hz
 

 54. 
The symbol for the period of a wave form is:
a.
F.
c.
T.
b.
P.
d.
W.
 

 55. 
The period of most AC waveforms is measured in units of:
a.
cycles.
c.
alternations.
b.
revolutions.
d.
seconds.
 

 56. 
The time (T) and the frequency (f) of an AC waveform are related as:
a.
inversely proportional.
c.
complimentary proportional.
b.
directly proportional.
d.
universally proportional.
 

 57. 
A square wave is a unique form of the rectangular pulse wave in that:
a.
the positive and negative halves are equal.
b.
the duty cycle is 50%.
c.
the wave is symmetrical.
d.
all of these
 

 58. 
The formula to convert degrees to radians is:
a.
degrees = mc058-1.jpg × radians.
c.
radians =mc058-2.jpg × degrees.
b.
180° = ð radians.
d.
all of these.
 

 59. 
The largest numerical value in the measurement of alternating current is:
a.
peak to peak.
c.
rms.
b.
average.
d.
peak.
 

 60. 
Troubleshooting an AC circuit can be performed with which of the following tools?
a.
analog voltmeter
c.
oscilloscope
b.
digital multimeter
d.
any of the above
 

 61. 
Superimposing an AC voltage of 3.54 Vrms with a DC source of 10 V results in a waveform that:
a.
peaks at 15 V.
c.
peaks at 20 V.
b.
peaks at 13.54 V.
d.
both B and C
 



 
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