PHYS 012A Lecture Notes - Lecture 24: Phasor, Voltage Source, Inductor
12 Jun 2018
School
Department
Course
Professor
Chapter 33 – AC Circuits
Electrical appliances in the house use alternating current (AC) circuits.
If an AC source applies an alternating voltage to a series circuit containing resistor, inductor, and
capacitor, what are the amplitude and time characteristics of the alternating current?
AC Circuits
- An AC circuit consists of a combination of circuit elements and a power source.
- The power source provides an alternating voltage, Dv.
- Notation note:
o Lower case symbols will indicate instantaneous values.
o Capital letters will indicate fixed values.
AC Voltage
- The output of an AC power source is sinusoidal and varies with time according to the following
equation:
o Δv = ΔVmax sin ωt
▪ Δv is the instantaneous voltage.
▪ ΔVmax is the maximum output voltage of the source.
• Also called the voltage amplitude
▪ ω is the angula feuency of the AC voltage.
-
- The current in any circuit driven by an AC source is an
alternating current that varies sinusoidally with time.
- f = 60 Hz. ~ ~
Resistors in an AC Circuit
- Consider a circuit consisting of an AC source and a resistor.
- The AC source is symbolized by
- ΔvR = DVmax= Vmax sin wt
- ΔvR is the instantaneous voltage across the resistor.
- Instantaneous current in te resistor is
find more resources at oneclass.com
find more resources at oneclass.com
- Current and voltage reach max values at the same time and are said to be in phase.
- Direction of current has no effect on the behavior of the resistor.
Phasor diagram
- A phasor is a vector whose length is proportional to the maximum value
of the variable it represents.
- The vector rotates counterclockwise at an angular speed equal to the
angular frequency associated with the variable.
- The projection of the phasor onto the vertical axis represents the
instantaneous value of the quantity it represents.
-
Rms Current and Voltage (rms → square, mean, squareroot)
find more resources at oneclass.com
find more resources at oneclass.com
Inductors in AC Circuit
Capacitors in an AC Circuit
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Electrical appliances in the house use alternating current (ac) circuits. An ac circuit consists of a combination of circuit elements and a power source. The power source provides an alternating voltage, dv: lower case symbols will indicate instantaneous values, capital letters will indicate fixed values. The current in any circuit driven by an ac source is an alternating current that varies sinusoidally with time. f = 60 hz. Consider a circuit consisting of an ac source and a resistor. Vr is the instantaneous voltage across the resistor. Current and voltage reach max values at the same time and are said to be in phase. Direction of current has no effect on the behavior of the resistor. A phasor is a vector whose length is proportional to the maximum value of the variable it represents. The vector rotates counterclockwise at an angular speed equal to the angular frequency associated with the variable.
