{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Lecture 31b

# Lecture 31b - Chapter 31 Simple AC circuits Resistor...

This preview shows pages 1–6. Sign up to view the full content.

Chapter 31: Simple AC circuits

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
R R V I R Resistor circuits Notation: Use lowercase for instantaneous values, Uppercase for peak values v R = ε = V R sin ω t i R = v R /R = I R sin ω t In an AC circuit, resistor voltage and current oscillate in phase . ε = ε m sin ω t
Capacitor circuits v C = ε = V C sin ω t i = dq/dt and q = Cv C : i C = ω CV C cos ω t which we write as: i C = ω CV C sin ( ω t + π /2) The current leads voltage by π /2 rads ICE ε = ε m sin ω t Current reaches peak value I C the instant the capacitor is fully discharged and v C =0. The current is zero the instant the capacitor is fully charged.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Capacitive Reactance Relationship between peak current and voltage in a capacitor I C = ω CV C , although they don’t happen at the same time. Define the capacitive reactance X C = 1/ ω C, then: I C = V C /X C This is analogous to Ohm’s Law for DC. at very high frequencies, X C approaches 0 and the capacitor acts like a wire. Units of X C :
Consider this circuit. The frequency of the AC source is adjusted, while its voltage amplitude is kept constant. The light bulb will glow brightest at A. High frequencies B. Low frequencies C. The brightness will be the same at all frequencies 1 C X C

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern