GEN PHYS FOR TECH ST
GEN PHYS FOR TECH ST PHYS 2102
Popular in Course
Popular in Physics 2
This 11 page Class Notes was uploaded by Alverta Blick III on Tuesday October 13, 2015. The Class Notes belongs to PHYS 2102 at Louisiana State University taught by Staff in Fall. Since its upload, it has received 6 views. For similar materials see /class/223005/phys-2102-louisiana-state-university in Physics 2 at Louisiana State University.
Reviews for GEN PHYS FOR TECH ST
Report this Material
What is Karma?
Karma is the currency of StudySoup.
Date Created: 10/13/15
3 Christia l lith Physics 2102 Lecture 17 DC circuits RC circuits Version 02202009 I Review 0 The potential of ideal emf devices does not depend on the current real emf devices have internal resistance 0 Kirchhoff s junction rule KJR The sum of the currents entering any junction is equal to the sum of the currents leaving the junction Resistors in parallel replace by equivalent resistance L L Reg JI1 Rj Resistors in series replace by equivalent resistance Req R 0 Ammeter measures current voltmeter measures voltage How to Solve Multi Loop Circuits Step I Simplify Compile Circuits Resistors V Key formula Vz R In series same current ReqZRj w W In parallel same voltage IReq ZIRj Wv W Capacitors QC V f w 81 RIEEliI R2 1 R l same Charge b E ICeq EllC f a s23 1 l same voltage L CquZC39j b Step II Apply Loop Rule Around every loop add 5 if you cross a battery from minus to plus if plus to minus and iR for each resistor Then sum to Zero 5 2 iR1 iR2 0 1 2 Conservation of ENERGY Step II Apply Junction Rule At every junction sum the ingoing currents and outgoing currents and set them equal 111z13 Conservation of CHARGE Step III Equations to Unknowns Continue Steps I III until you have as many equations as unknowns Given 5 2 LR R2 1 62 i1R1 12 R2 2 0 and 139 i1i2 Solve for i1 i2 Monster Mazes If all I GSiStOI S haVe a If all capacitors have a resistance of 49 and all capacitance of 6MB and batteries are ideal and all batteries are ideal haVe an emf 0f 4V and have an emf of 10V what iS the Clll l fiht what is the charge on through R capacitor C It l 39l I l V l Z 39 3 I gt NV T T lr i f lquot f i ii RC Circuits Charging a Capacitor In these circuits current will change for a while and then stay constant We want to solve for current as a function of time it The charge on the capacitor will also be a function of time qt The voltage across the resistor and the capacitor also change with time To Charge the capacitor close the switch on a E VRtVCt 0 l S H l E 0 L E dqtdt R qtC 0 A differential equation for qt The solution is qt CEle tRC And then 1 t dedt ER e tRC l 1390 Time constantRC E R 1F RC Circuits Discharging a Capacitor I 3 Assume the switch has been closed I R on a for a long time the capacitor all will be charged with QCE Then close the switch on 92 charges nd their way across the circuit establishing a current VRVC0 itRqtC0 gt dqdtRqtC0 i R Solution qtq0e tRCCEe VRC 1 t dqdt q RC e tRC ER e tRC C o a H Exponential discharge 0 E ER r gr Summary 0 Technique to solve multiloop circuits 1 Simplify compile circuits 2 Apply loop rule 3 Equations to unknowns 0 RC circuits simple circuit with timevarying current time constant is 17 RC Charging a capacitor qt CE1 e tRC Discharging a capacitor qtCEe tRC