### Create a StudySoup account

#### Be part of our community, it's free to join!

Already have a StudySoup account? Login here

# PHY 184 Week 7 PHY 184

MSU

### View Full Document

## About this Document

## 2

## 0

## Popular in Physics for Scientists and Engineers II

## Popular in Physics

This 4 page Class Notes was uploaded by Cameron Blochwitz on Sunday October 16, 2016. The Class Notes belongs to PHY 184 at Michigan State University taught by Oscar Naviliat Cuncic in Fall 2016. Since its upload, it has received 2 views. For similar materials see Physics for Scientists and Engineers II in Physics at Michigan State University.

## Similar to PHY 184 at MSU

## Popular in Physics

## Reviews for PHY 184 Week 7

### What is Karma?

#### Karma is the currency of StudySoup.

#### You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!

Date Created: 10/16/16

PHY 184 Week 7 Notes-DC Circuits 10/10-10/13 Most practical circuits cannon be resolved into series or parallel systems of capacitors and resistors o To handle this we use Kirchhoff’s rules A Junction is a place where 3+ wires connect o Each connection between 2 junctions is called a branch Each branch has the same current within the branch A Loop in a current is any set of connected wires forming a closed path o You can get back to where you started Kirchhoff’s Junction Rule The sum of currents entering a junction equals the sum of currents leaving the junction Positive terms enter, negative terms exit n i =0 o k=1k Consider a Junction with current i e1tering and i an2 i lea3ing i =i +i o 1 2 3 This is a direct result of conservation of electric charge o Junctions cannot store charge Kirchhoff’s Loop Rule The potential difference of a complete loop is equal to 0 o Direction is irrelevant All that matter is that you follow the same conventions around the loop Resistors o Along Current -iR o Opposite Current +iR Battery o Same as emf +V o Opposite emf -V Emf goes from negative to positive The direction you travel around the loop and the direction of the current are totally arbitrary o Will not change final result outside of a minus sign General Observations Voltage drop is a linear relation Kirchhoff’s Junction Rule established linear relations between currents in the junctions o Coefficients are +1 or -1 If a circuit contains only batteries and resistors Kirchhoff’s Loop Rule established other linear relations For Linear circuits we can determine the voltage by knowing the current in each branch A circuit with n junction has n-1 independent equations A circuit with 4 junctions and three loops have 3 equations from junctions and 3 from loops o Choose the smallest loops to work on Analysis of Linear Circuits Choose a direction for all currents Choose loops and a way to travel them Write the n-1 relations for currents Look at ΔV along the selected loops and write the loop and write the loop rule Finally, you have N equations and N unknowns o You can solve the equation Devices Ammeter measures current o Is in series and has low resistance A Voltmeter Measures Voltage o Is in parallel and has high resistance RC Circuits An RC circuit has both a resistor and a capacitor o They will vary over time Charging a Capacitor We start with the capacitor uncharged When the switch is closed current begins to flow building the charge on the capacitor o This creates a potential difference in the capacitor When the capacitor is fully charged no current will flow o Potential from the capacitor and the battery are equal When charged the charge on the plates is q=CV To Calculate the current in the circuit we use the KLR for a single loop Start at a given point with arbitrary current and loop directions Applying KLR V−i t)R− q(t=0 o C By definition dq(t) o (t= dt So we can rewrite KLR as V− dq(t− q(t=0 o dt C Which can be rearranged to dq(t) 1 q o ( ) = − ( ) () dt R c Integrating this and solving for q gives −t o qt)=qmax(1−eRC)¿ o τ=RC qmaxCV o Current flowing though the circuit is the time derivative −t (t= V eRC o r i0= V R Potential difference across a capacitor can be written RC o V t)=V (1−e ) Discharging a Capacitor Consider the circuit containing one resistor and one capacitor o When disconnected from a battery the charged capacitor will begin to discharge until depleted Vr+V i0 q(t) (t)R+ C =0 Solution is therefo−t RC o q(t=q 0 Current is q o it)= RC

### BOOM! Enjoy Your Free Notes!

We've added these Notes to your profile, click here to view them now.

### You're already Subscribed!

Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'

## Why people love StudySoup

#### "There's no way I would have passed my Organic Chemistry class this semester without the notes and study guides I got from StudySoup."

#### "I bought an awesome study guide, which helped me get an A in my Math 34B class this quarter!"

#### "There's no way I would have passed my Organic Chemistry class this semester without the notes and study guides I got from StudySoup."

#### "Their 'Elite Notetakers' are making over $1,200/month in sales by creating high quality content that helps their classmates in a time of need."

### Refund Policy

#### STUDYSOUP CANCELLATION POLICY

All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email support@studysoup.com

#### STUDYSOUP REFUND POLICY

StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here: support@studysoup.com

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to support@studysoup.com

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.