RC Circuits problems
- 1. What is the value of the hypotenuse of a right triangle whose sides are 12 and 18?
Options- A. 4.24
- B. 3.46
- C. 2.16
- D. 21.63 Discuss
Correct Answer: 21.63
- 2. A capacitor with 150 Ω of capacitive reactance is across an ac source. The impedance, expressed in polar form, is
Options- A. Z = 150
- B. Z = 150∠90°Ω
- C. Z = 150 ∠?90°Ω
- D. Z = 150∠180°Ω Discuss
Correct Answer: Z = 150 ∠?90°Ω
- 3. A 2 kΩ resistor is in series with a 0.015 µF capacitor across a 15 kHz ac source. What is the magnitude of the total impedance and the phase angle?
Options- A. 73.4 Ω and ? = ?19.5°
- B. 707 Ω and ? = ?19.5°
- C. 2121 Ω and ? = ?19.5°
- D. 734 Ω and ? = ?38.9° Discuss
Correct Answer: 2121 Ω and ? = ?19.5°
Explanation:
Xc = 1/2?fC = 707 ?
Z = R - jXc = 2000 - j(707)
|z| = sqrt(R*R + Xc*Xc) = 2121 ?
Phase angle = arctangent(Xc/R) = 19.5°
- 4. In a series RC circuit, when the frequency and the resistance are halved, the impedance
Options- A. doubles
- B. is halved
- C. is reduced to one-fourth
- D. cannot be determined without values Discuss
Correct Answer: cannot be determined without values
- 5. When the frequency of the voltage applied to a series RC circuit is increased, the phase angle
Options- A. increases
- B. decreases
- C. remains the same
- D. becomes erratic Discuss
Correct Answer: decreases
- 6. A 120 Ω resistor is in parallel with a capacitor with a capacitive reactance of 40 Ω. Both components are across a 12 V ac source. What is the magnitude of the total impedance?
Options- A. 37.9 Ω
- B. 3.7 Ω
- C. 14,400 Ω
- D. 4,800 Ω Discuss
Correct Answer: 37.9 Ω
- 7. The voltages in Problem 4 are measured at a certain frequency. To make the capacitor voltage greater than the resistor voltage, the frequency
Options- A. must be increased
- B. must be decreased
- C. is held constant
- D. has no effect Discuss
Correct Answer: must be decreased
- 8. Complex numbers can be added and subtracted but not multiplied or divided.
Options- A. True
- B. False Discuss
Correct Answer: False
- 9. Positive numbers can be represented by points to the right of the origin on the horizontal axis of a graph.
Options- A. True
- B. False Discuss
Correct Answer: True
- 10. A complex number represents a phasor quantity.
Options- A. True
- B. False Discuss
Correct Answer: True
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