MECH 1100 Quiz 4 Practice

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1 Name: Class: Date: MECH 1100 Quiz 4 Practice True/False Indicate whether the statement is true or false. 1. An advantage of a of a three-phase induction motor is that it does not require starter windings. 2. The difference in the synchronous speed of the stator field and the rotor speed of a motor is called the differential speed. 3. A sychronous motor can be used when constant speed is required. 4. A sine wave s frequency equals the reciprical of its period 5. The higher a sine waves frequency, the shorter it s period. 6. A sine wave s peak value is smaller than its RMS value. 7. RMS is another name for peak V PP is approximately equal to 2.5V RMS 9. The period of a 5 Hz wave form is 200ms. 10. Current flows both ways simultaneously in an AC circuit. 11. Only frequency increase with the speed of an AC generator. 12. Kirchhoff s voltage law can be used with resistive circuits. 13. Capacitance is the ability to store voltage. 14. If the distance between the plates of a capacitor increases, the capacitance decreases. 15. A capacitor can fully charge in one time constant. 16. Capacitance is a capacitor s ability to store resistance. 17. When two capacitors are connected in series across a dc source, the smallest capacitor drops the largest voltage. 18. A capacitor will fully charge in about five time constants. 19. Efficient filtering is directly related to RC time constant. 1

2 Name: 20. Leakage through a capacitor is undesirable. Multiple Choice Identify the choice that best completes the statement or answers the question. 21. A sine wave with a frequency of 13kHz is changing at a faster rate than a sine wave with a frequency of a. 18kHz c. 12,000 Hz b. 16,000 Hz d. 1.5 MHz 22. When a sine wave has a frequency of 60Hz, in 20s it goes through a. 20 cycles c cycles b..333 cycles d. 3 cycles 23. If the peak value of a sine wave is 12V, the rms value is a V c. 8.48V b. 6V d. 24V 24. If the peak value of a sine wave is 9V, the rms value is a. 6.36V c. 8.24V b d. 4.5V 25. The average value of a 20V peak sine wave over one complete cycle is a. 10V c. 0V b. 20V d. 40V 26. The average half-cycle value of a sine wave with a 10V peak is a. 7.07V c V b. 15.7V d. 6.37V 27. The instantaneous value of a 5A peak sine wave at a point 45 from its positive-going zero crossing is a. 3.54V c. 3.54A b. 7.07A d. 7.07A 28. Which one of the following can be measured from points B to F? a. the frequency c. the period b. the angle d. the peak-to-peak voltage 2

3 Name: 29. V PP is measured between points and _. a. A and B c. C and H b. G and I d. D and F 30. Which of the following can be measured from point E to point F? a. the RMS voltage c. the peak to peak voltage b. the peak voltage d. one cycle of voltage 31. Calculate V R2 a. 6.84V PP c. 6.84V P b V P d. 4.84V P 3

4 Name: 32. What is the approximate peak input voltage? a. 28.3V P c. 20V P b. 14.1V P d. 20V P 33. Calculate V R1 a. 21.4V P c. 13.2V P b. 6.84V P d. 13.7V P 34. What is the instantaneous voltage across R 1 at an angle of 22? a. 8.03V c. 2.56V b. 12.0V d. 20.3V 4

5 Name: 35. Calculate R T a. 1.13kΩ c. 4.77kΩ b. 4.7kΩ d. 6.2kΩ 36. Calculate the instantaneous voltage across R 1 at 122 a. 18.2V c. 11.2V b. 5.8V d. 11.6V 37. A 60Hz sine wave completes cycles every 10 seconds. a. 6 c. 1/16 b. 10 d A sine wave s instantaneous voltage is 0V at degrees/ a. 0 c. 360 b. 180 d. all of these 39. What is one time constant of a 4.7µF in series with a 22kΩ resister? a ms c. 10.3ms b. 1.03ms d. 103ms 40. How long will it take a 0.047µF capacitor to fully charge through a 100kΩ resister? a. 2.35s c. 23.5ms b ms d. 235ms 41. If a 4.7µF capacitor operates at 10kHz, X C =. a. 339Ω c. 3.39Ω b. 294µΩ d. infinite resistance 5

6 Name: 42. At what frequency is a 2000pF capacitor operating if its reactance is 745Ω? a. 107kHz c. 1.01kHz b. 10.1kHz d. 1010Hz 43. If a 22µF capacitor is coneected to a 15V 400Hz source, its current equals. a. 55mA c. 829mA b. 18.1mA d. 1.81A 44. What is the capacitance that stores 1.175µC of charge and drops 25V? a µF c. 4.7µF b. 0.47µF d. 47µF 45. How much stored charge in a 0.47µC capacitor that drops 18V? a. 846µF c. 8.46µF b. 84.6µF d µF 46. If a 0.047µF capacitor operates at 220kHz, X C equals. a. 15.4kΩ c. 150Ω b. 1.54kΩ d. 15.4Ω 47. If a 47µF capacitor is connected to a 20V, 400Hz source, the current is. a. 425A c. 8.51A b. 2.36A d A Problem 48. Be able to define Amplitude, Cycle, Degree, Duty Cycle, Fall time, Frequency, Function generator, Fundamental Frequency, Harmonics, Hertz, Induction motor, Instantaneous value, Oscillator, Oscilloscope, Peak-to-Peak value, Peak value, Period, Periodic, Phase, Pulse, Pulse Width, Radian, Ramp, Rise time, rms value, Sine Wave, Squirrel Cage, Synchronous Motor, Waveform 6

7 Name: 49. Calculate V RMS, I RMS and P RMS V RMS = I RMS =_ P RMS = _ 50. Interpret the oscilloscope to find V P, V PP, Period, Frequency and duty cycle. V P = V PP = P = f = Duty cycle = 7

8 Name: 51. Know the key terms: Bypass, Capacitance, Capacitive reactance, Capacitor, Charging, Coupling, Decoupling, Dielectric, Dielectric Constant, Dielectric Strength, Exponential, Farad, Filter, Instantaneous power, RC time constant, Reactive Power, Ripple Voltage, Temperature coefficient, Transient time, True Power, VAR. 52. Calculate the total capacitance, the reactants for each capacitor and the voltage drop across C 2 in RMS. Total Capacitance = X C1 = X C2 =_ V C2 = 53. Calculate the total capacitance, the reactants for each capacitor and the voltage drop across C 8 in RMS. Total Capacitance = X C8 = X C9 = X C10 = V C8 = 8

9 Name: 54. Calculate the time constant τ and the instantaneous dis-charging voltage at 1 time constant using RMS voltage. τ = V ins tan tan eous = 55. Calculate the time constant τ and the instantaneous charging voltage at 1 time constant using RMS voltage. τ = V ins tan tan eous = 9

10 MECH 1100 Quiz 4 Practice Answer Section TRUE/FALSE 1. ANS: T 2. ANS: F Slip 3. ANS: T 4. ANS: T 5. ANS: T 6. ANS: F 7. ANS: F 8. ANS: T 9. ANS: T 10. ANS: F 11. ANS: F 12. ANS: T 13. ANS: F 14. ANS: T 15. ANS: F 16. ANS: F 17. ANS: T 18. ANS: T 19. ANS: T 20. ANS: T MULTIPLE CHOICE 21. ANS: C 22. ANS: C 23. ANS: C 24. ANS: A 25. ANS: C 26. ANS: D 27. ANS: C 5sin(45) 28. ANS: C 29. ANS: D 30. ANS: B 31. ANS: C 1

11 32. ANS: A 33. ANS: A 34. ANS: A 35. ANS: D 36. ANS: A 37. ANS: D 38. ANS: D 39. ANS: D 40. ANS: C 41. ANS: C 42. ANS: A 43. ANS: C 44. ANS: A 45. ANS: C 46. ANS: D 47. ANS: B PROBLEM 48. ANS: see your book 49. ANS: V RMS = 84.84V I RMS = 56.5mA P RMS = 4.8W 50. ANS: V P = 120V V PP = 240V Period = 16.3ms f = 60 Hz Duty cycle = 36.8% 51. ANS: See your book 52. ANS: Total Capacitance = 30µF X C1 =35.36Ω X C2 =53.05Ω V C2 =50.9V 2

12 53. ANS: Total Capacitance = 127µF X C8 =132.6Ω X C9 =56.43Ω X C10 =44.2Ω V C8 =60V 54. ANS: τ = V ins tan tan eous = ANS: τ = 4.23 V ins tan tan eous =

Any wave shape can be reproduced by the sum of sine waves of the appropriate magnitude and frequency.

Any wave shape can be reproduced by the sum of sine waves of the appropriate magnitude and frequency. How do we use an oscilloscope? Measure signals with unknown wave shapes and frequency other than 60 Hz sine waves and dc. To get a picture of the waveform. Distortion? Phase duration? Magnitude Any wave