Deck 8: Introduction to Alternating Current and Voltage

Question 1

What is the instantaneous voltage at 42° on a 230 VP sine wave?

A) 154 V
B) 115 V
C) 149 V
D) 76.1 V

Answer 1

154 V

Question 2

7.07 V_PP is approximately equal to 2.5 V_RMS

Answer 2

True

Question 3

An ac current is inversely proportional to an ac Voltage.

Answer 3

False

Question 4

A sineW aveʹs frequency equals the reciprocal of its period.

Question 5

The RMS value of a sine wave means__________

A) the root mean square value
B) the heating effect of an ac generator of the same voltage
C) the same as I_PP* R
D) the same as I_P * R

Question 6

The higher a sineW aveʹs frequency, the shorter its period.

Question 7

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

Question 8

Kirchhoffʹs voltage law can be usedW ith resistive ac circuits.

Question 9

One complete sine wave contains 360°

Question 10

The term RMS stands for ʺroot-mean-square.ʺ

Question 11

Current flows both ways simultaneously in an AC circuit.

Question 12

VPP is measured between points ________ in Figure 8-1.

A)A and B
B)D and F
C)G and I
D)C and H

Question 13

A sineW aveʹs peak value is smaller than its RMS value.

Question 14

Which one of the following represents the value at point G in Figure 8-1?

A)the period
B)the peakVoltage
C)the frequency
D)the RMSVoltage

Question 15

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

Question 16

Rise time, fall time, and duty cycle are all terms associatedW ith sineW ave measurement.

Question 17

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

Question 18

which of the following can be measured from points B to F in Figure 8-1?

A)the peak-to-peakVoltage
B)the frequency
C)the period
D)the angle

Question 19

Only frequency increases With the speed of an AC generator.

Question 20

Which point in Figure 8-1 is 180° away from point E?

A)A
B)B
C)C
D)D

Question 21

Calculate the total power dissipation in the circuit in Figure 8-2.

A) 182 mW
B) 64.5 mW
C) 9.12 mW
D) 45.6 mW

Question 22

Calculate I_T in Figure 8-2.

A) 9.12 mAPP
B) 3.22 mAPP
C) 6.44 mAPP
D) 4.55 mAPP

Question 23

In Figure 8-1, if the time from point A to H is 60 μs the frequency is ________.

A)16.7 kHz
B)25 kHz
C)50 kHz
D)More information is required to calculate the frequency.

Question 24

What is the approximate instantaneous voltage at 37° on a 169 V_P sine wave?

A) 239 V
B) 135 V
C) 102 V
D) 119 V

Question 25

Find R_T in Figure 8-2.

A) 4.7 kΩ
B) 4.77 kΩ
C) 6.2 kΩ
D) 1.13 kΩ

Question 26

Calculate V_R1 in Figure 8-2.

A) 6.84 V_P
B) 13.2 V_P
C) 13.7 V_P
D) 21.4 V_P

Question 27

In Figure 8-2, what is the instantaneous voltage across R₁ at an angle of 22°?

A) 8.03 V
B) 2.56 V
C) 20.3 V
D) 12.0 V

Question 28

Figure $8 < 2$

-If you measure about 56 V_PP across the source in Figure 8-2 , what is the trouble?

A) R₁ is open.
B) Both R₁ and R₂ are open.
C) R₂ is open.
D) There is no trouble. 56 V_PP is a normal measurement for the source voltage.
E) any of these

Question 29

In Figure 8-1,W hich of the following can be measured from point E to point F?

A)the peak to peakVoltage
B)the peakVoltage
C)the RMSVoltage
D)one cycle ofVoltage

Question 30

Figure $8 < 2$

-In Figure 8-2, if you look at V_R1 with an oscilloscope and you find no trace, a possible trouble might be that_________

A) R₂ is shorted
B) R₂ is open
C) R₁ is open
D) the resistance of R₂ has changed

Question 31

Find P_R1 in Figure 8-2.

A) 0 W
B) 196 mW
C) 48.9 mW
D) 97.8 mW

Question 32

Figure $8 < 2$

-If R₁ shorts in Figure 8-2, V_R2__________

A) decreases
B) remains the same
C) increases

Question 33

If a rectangular waveʹs pulse width is 50 μS and its frequency is 4 kHz, its duty cycle is ________.

A)98.75%
B)20%
C)1.25%
D)80%

Question 34

Calculate V_R2 in Figure 8-2.

A) 6.84 V_PP
B) 6.84 V_P
C) 13.15 V_P
D) 4.84 V_P

Question 35

In Figure 8-2 , what is the instantaneous voltage across R₁ at 122°?

A)11.2V
B)11.6V
C)5.8V
D)18.2V

Question 36

In Figure 8-1, the time from point C to E is called ________.

A)a cycle
B)the period
C)peakVoltage
D)a half-cycle

Question 37

The time required by a 10 V square wave to change from 1 V to 9 V is known as the ________.

A) fall time
B) pulse width
C) period
D) rise time

Question 38

What is the approximate peak input voltage to the circuit in Figure 8-2?

A) 20 V_P
B) 28.3 V_P
C) 10 V_P
D) 14.1 V_P

Question 39

What is the instantaneous voltage at 284° on a 22 V_PP sine wave?

A)10.7V
B)0.33V
C)-2.66V
D)-10.7V

Question 40

Figure $8 < 2$

-VR₂ _________if R₁ opens in Figure 8-2

A) decreases
B) remains the same
C) increases

Question 41

The value of a AC sine wave at any instant can be represented by:

A) a phasor whose angle and magnitude are representative of the AC signal.
B) the formula V_i=V_p* sin θ
C) a graph of the voltage or current vs. the angular measurement.
D) all of these.

Question 42

A square wave is a unique form of the rectangular pulse wave in that:

A)the duty cycle is 50%.
B)the positive and negative halves are equal.
C)the Wave is symmetrical.
D)all of these

Question 43

Superimposed DC and AC voltages mean the two voltages are combined:

A)in series-parallel aiding or opposing.
B)in parallel aiding or opposing.
C)in series aiding or opposing.
D)all of these

Question 44

The period of most ACW aveforms is measured in units of:

A)alternations.
B)seconds.
C)cycles.
D)revolutions.

Question 45

A 60 Hz sine wave completes ________ cycles every 10 seconds.

A)600
B)1/16
C)10
D)6

Question 46

In a two-resistor series circuit V_R1=6.5 V_RMS and V_R2=3.2 V_RMS. The source voltage is_____

A)9.19V_P
B)4.53V_P
C)9.7V_P
D)13.7V_P

Question 47

The time (T)and the frequency (f)of an ACW aveform are related as:

A)universally proportional.
B)directly proportional.
C)inversely proportional.
D)complimentary proportional.

Question 48

What is the instantaneous voltage at 17° on a 169 V_P sine wave?

A) 49.4 V
B) 80.5 V
C) 161 V
D) 98.8 V

Question 49

A sine wave's instantaneous voltage is 0 V at _______degrees.

A) 360
B) 0
C) 180
D) all of these

Question 50

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) 12.5 Hz
B) 25 Hz
C) 50 Hz
D) More information is needed.

Question 51

An oscilloscope's seconds/division switch is set on 20 $\mu \mathrm { s } / \mathrm { cm }$ . If the trace is 7.5 cm long, what is the period?

A) 150 $\mu \mathrm { s }$
B) 1.5
C) 5 $\mu \mathrm { s }$
D) 0.0015 s

Question 52

A 10 V_P sine wave is equal to________

A) 20 V_PP
B) 100 V_PP
C) 5 V_PP
D) none of the above

Question 53

If the period of a square wave is 22 ms,What is its frequency?

A)45.5 kHz
B)45.5 Hz
C)22 kHz
D)22 Hz

Question 54

The average value of a rectangular pulse wave is calculated as:

A) Vavg =0.637 V_p
B) Vavg = Vbaseline + (duty cycle)*V_p
C) Vavg =1.57 V_p .
D) Vavg = Vbaseline +V_p.

Question 55

A formula for V_RMS is________

A) 2 *V_P
B) 2.8 *V_P
C) 0.707 *V_P
D) 0.707 *V_PP

Question 56

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) 0.008 V
B) 50 mV
C) 1.6 mV
D) 80 mV

Question 57

The AC sine wave varies from zero to its maximum value in accordance with:

A)a trigonometric relationship.
B)a geometric progression.
C)an algebraic function.
D)a mathematical formula.

Question 58

If a 10 $k \Omega$ resistor carries 5 mA_RMS of current, its voltage drop equals_________

A) 5 V_RMS
B) 50 V_RMS
C) 7.07 V_RMS
D) 70.7 V_RMS

Question 59

The symbol for the period of a Wave form is:

A)W.
B)T.
C)P.
D)F.

Question 60

A 12 V_P sine wave equals_______

A) 8.48 V_RMS
B) 7.64 V_AVG
C) 24 V_PP
D) all of these

Question 61

Superimposing an AC voltage of 3.54 Vrms with a DC source of 10 V results in a wave form that:

A)peaks at 15V.
B)peaks at 13.54V.
C)peaks at 20V.
D)both B and C

Question 62

The squareW ave is made up of:

A)just the fundamental frequency.
B)the fundamental frequency and both the odd and even harmonics.
C)the fundamental frequency and all the even harmonics.
D)the fundamental frequency and all the odd harmonics.

Question 63

Troubleshooting an AC circuit can be performed with which of the following tools?

A)digital multimeter
B)analog voltmeter
C)oscilloscope
D)any of the above

Question 64

The largest numerical value in the measurement of alternating current is:

A)peak to peak.
B)rms.
C)average.
D)peak.

Question 65

While troubleshooting a circuit the voltage seems to be zero;What if any adjustment should be checked on the oscilloscope?

A)trigger level
B)AC/GND/DC switch
C)focus setting
D)time division setting

Question 66

This display in Figure 8-3 illustrates maladjustment of which control on the oscilloscope?

A)coupling
B)trigger level
C)intensity
D)volts/div