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Chapter Analysis
Advanced23 pages • EnglishQuick Summary
This chapter on Alternating Current covers the principles of alternating voltage and current focused on resistive, inductive, and capacitive components. It introduces the concept of phasors and discusses the importance of rms values in AC circuits to express power. The chapter explains the behavior of AC when applied to RLC circuits and the phenomenon of resonance. Additionally, it addresses transformers and their role in voltage transformations.
Key Topics
- •Alternating voltage and current fundamentals
- •Phasor representation
- •RMS values and power calculations
- •AC applications to resistors, inductors, and capacitors
- •Series RLC circuit and resonance
- •Transformers and voltage transformation
Learning Objectives
- ✓Understand the basic concepts and principles of alternating current and voltage.
- ✓Analyze and calculate electrical quantities using phasors and rms values.
- ✓Explain the behavior of AC circuits with resistive, capacitive, and inductive components.
- ✓Describe the resonance phenomenon in RLC circuits and its applications.
- ✓Gain insights into the operation and efficiency of transformers in electrical systems.
Questions in Chapter
A pure inductor of 25.0 mH is connected to a source of 220 V. Find the inductive reactance and rms current in the circuit if the frequency of the source is 50 Hz.
Answer: The inductive reactance is 7.85 ohms and the rms current in the circuit is 28 A.
Page 184
A 15.0 µF capacitor is connected to a 220 V, 50 Hz source. Find the capacitive reactance and the current (rms and peak) in the circuit.
Answer: The capacitive reactance is 212 ohms, the rms current is 1.04 A, and the peak current is 1.47 A.
Page 186
Suppose the frequency of the source in the previous example can be varied. What is the frequency of the source at which resonance occurs?
Answer: The frequency at which resonance occurs is 35.4 Hz.
Page 193
Additional Practice Questions
Explain the concept of 'power factor' in AC circuits and its significance.
mediumAnswer: Power factor is the measure of how effectively the current is being converted into useful work output. It is the cosine of the phase angle between the voltage and current waveforms in an AC circuit. A power factor of 1 means all the power is effectively converted into useful work.
What are the differences in the behavior of AC and DC in a resistor?
easyAnswer: In a resistor, both AC and DC have the same relationship of V = I * R, meaning they both experience voltage drop across resistive components. However, in AC circuits, the current and voltage are sinusoidally varying, while in DC circuits they are constant.
How does a transformer step-up voltage, and why does it not create energy?
hardAnswer: A transformer steps-up voltage by having more turns in the secondary coil than in the primary. Although the voltage is increased, energy is conserved because as voltage increases, the current decreases proportionally, maintaining power balance.
Describe resonance in an RLC circuit and its practical applications.
mediumAnswer: Resonance in an RLC circuit occurs when the inductive reactance equals the capacitive reactance, resulting in a maximum current amplitude at resonant frequency. This is applied in radio tuning and filters.
What are the implications of using AC over DC for large scale power distribution?
mediumAnswer: AC is preferred for large scale power distribution because it can be easily transformed to different voltages, allowing economical transmission over long distances with reduced energy loss.