1. AC Circuits
12.2

2. This Week & Next We begin the study of AC Circuits
We begin the next unit
Friday
Same thing
Quiz, Of course

3. 2
Problems
???

4. It’s the current! Note-1: The voltages across each element   i i i
Note-1: The voltages
across each element
are not the same!

5. The Resistor – A LINEAR Circuit Element
Ohm’s Law always applies
V=iR
In this case:

6. Phase Diagram

7. Phase these two voltages have the same amplitude but they do not have these values at the same time!
instantaneous
voltage
leads lags V0
time

8. Different amplitudes Different Phase
Green lags the grey by 90 degrees

9. Keep In Mind
If a circuit has a sinusoidal voltage applied to it the you should expect that all voltages across the various elements will also vary sinusoidally but will have different amplitudes and phase relationships between them

10. For the Inductor
Note that at t=0, DV/Dt is a maximum so back emf is a minimum.
From this graph you can see that the current lags the voltage by 90 degrees.
A possible relationship between V and I could be V=IXL
XL has the units of OHMS and is called the inductive reactance.

11. Phase Diagram for Inductor
More on Inductor
Phase Diagram for Inductor
The current lags the voltage by 90 degrees.

12. And so it goes for the Capacitor

13. Capacitor
Circuit Diagram
Factoids
Note that at t=0, DV/Dt is a maximum so current is also a maximum.
From this graph you can see that the current leads the voltage by 90 degrees.
A possible relationship between V and I could be V=IXC
XC has the units of OHMS and is called the capacitive reactance.

14. Read in the Textbook

15. The Approach – Again, Read the BookXL R XC

16. The Voltages

17. The Real Deal