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# Chapter 31: AC Circuits

Alternating Current (AC) circuits are circuits where the current and the voltage vary sinusoidally in time (in comparison with DC circuits where the voltage and current are constant). AC is the type of current you get from wall outlets; the current switches direction 60 times a second (60 Hz current). With AC, we begin the study of circuits with non-linear circuit elements such as capacitors, inductors and transformers, which are the back-bone of analog and power electronics.

# Table of Contents

## Illustration

- Illustration 31.1: Circuit Builder.
- Illustration 31.2: AC Voltage and Current
- Illustration 31.3: Transformers.
- Illustration 31.4: Phase Shifts.
- Illustration 31.5: Power.
- Illustration 31.6: Voltage and Current Phasors.
- Illustration 31.7: RC Circuits and Phasors.
- Illustration 31.8: Impedance and Resonance.

## Explorations

- Exploration 31.1: Amplitude, Frequency, and Phase Shift.
- Exploration 31.2: Reactance.
- Exploration 31.3: Filters.
- Exploration 31.4: Phase Angle and Power.
- Exploration 31.5: RL Circuits with Phasors.
- Exploration 31.6: RLC Circuits with Phasors.
- Exploration 31.7: RLC Circuits and Resonance.
- Exploration 31.8: Damped RLC.

## Problems

- Problem 31.1: Power of light bulbs (with switches).
- Problem 31.2: Transformer.
- Problem 31.3: Power and resistive loads.
- Problem 31.4: Identify the unknown element.
- Problem 31.5: Determine value of component.
- Problem 31.6: RC series circuit.
- Problem 31.7: RL Series circuit.
- Problem 31.8: RC oscillations.
- Problem 31.9: Find power with R from V and I graphs.
- Problem 31.10: Speaker system design.
- Problem 31.11: Determine value of capacitance and power in RC circuit.
- Problem 31.12: Determine value of inductor and power in RL circuit.
- Problem 31.13: Rank resistors in switched RLC circuits.
- Problem 31.14: Resonance curve.