1. AC Circuits

2. Resistors behave the same in an AC circuit
Vrms=Irms R V R

3. The voltage across a capacitor lags the current.
Vrms = Irms XC
Capacitive Reactance
XC = 1/(2πfC) (Ω)

4. What is the rms current in a circuit with a 20microF capacitor connected to a 120V AC source at 60Hz?
V=120V
F=60Hz
C = 20μF

5. The voltage across an inductor leads the current.
Vrms = Irms XL
Inductive Reactance
XL = 2πfL (Ω)

6. What is the rms current in a circuit with a 10mH inductor connected to a 120V AC source at 60Hz?
V=120V
F=60Hz
L=10mH

7. Putting them all together (LRC)
V=120V
F=60Hz L C R
VR=I R
VC= I XC
VL= I XL
Vtot = I Z
(Impedance)Z= √R2 + (XC – XL)2

8. In the LRC circuit below: 1)what is the impedance 2) what is the current?
V=120V
F=60Hz
L=10mH
C = 20μF
R = 100 Ω

9. Phase Angle Is the Voltage leading or lagging the current?
If XC > XL The voltage is lagging the current
If XC < XL The voltage is leading the current
Tan φ = (XL – XC) /R
V=120V
F=60Hz
L=10mH
C = 20μF
R = 100 Ω

10. Power P = Irms Vrms Cos φ (W)
What is the power consumed by this circuit?
V=120V
F=60Hz
L=10mH
C = 20μF
R = 100 Ω