Page 1 of 3PHYS1120 Exam II reviewThings to remember for PHYS1110: algebra, trig (sin, cos, ..)vector math, especially vector addition, Fnet = ma problems, free-body diagramsExam I Material : E-fields, Gauss's LawChapter 23 Voltage = Electric Potential- Definition of voltage: fof qiUV E drqDD � = - ��vv , of qU q VD = D- - V E xD = D ( if E = constant and E xDrrP ) , xd VEd x= -- Voltage is electrical height, E-field is slope- if r ED ^rv, V 0D = , equipotential lines - Voltage due to a point charge Q: k QV(r)r=- Voltage due to many charges: iii iik Q k dqV(r) Vr r= = =� ��- Work done by external agent to move charge q through a voltage difference--V =ext of qW U q V= D = D . If charge q falls through a voltage difference--V,KE PE q VD = D = D- Units of electron volts (eV). Ch.24 Capacitors- capacitance QCV�10/11/2009 M.Dubson PHYS1120 Notes ©University of Colorado at BoulderEhi V lo V+Q–QEV = -Vdarea AdRI-Vhi Vlo Vin series:R1R2=Rtot = R1 + R2R1R2=in parallel:Page 2 of 3- C depends only on size and shape: oACde=- Adding capacitors in series and parallel.- stored energy = 221 1 1 QU Q V C V2 2 2 C= = =- energy per volume = 2oU 1u Evolume 2= = e. Ch.25, 26 Current and Circuits - d QId t=, dIJ n q vA= = (where n = #carriers/volume, vd = drift speed)1J E E= s =r , - = resistivity = measure of internal friction, depends on composition- Ohm's Law: V I R (where R = constant)D = �- Resistance of a resistor: LRAr= - 22W Vpower P I V I Rt RD= = = =D- Equivalent Resistance: tot1 21R1 1R R=+10/11/2009 M.Dubson PHYS1120 Notes ©University of Colorado at Boulderarea ALPage 3 of 3Things that are always true in circuits:- elements in series always have the same current:- elements in parallel always have the same voltage:- voltage change along an unbroken ideal wire is zero (sincewe assume Rwire = 0 ) : wire wireV I R I 0 0D = = � =- ideal battery means constant -V for any current, current depends on the circuit- K's Current Law (Junction Law) total current into junction = total current out ofjunction : 1 2 3I I I= +- K's Voltage Law (Loop Law): total voltage changearound any closed loop is zero- Ammeters and VoltmetersTo prepare for Exam 1:- Review Concept Tests, CAPA problems, and Tutorial HW. (Read question and try to remember reasoning that gets to the answer)- Prepare your formula sheet.- Take the practice exam.- It is no good to memorize answers. You have to understand and remember how you got the answers.10/11/2009 M.Dubson PHYS1120 Notes ©University of Colorado at BoulderR1R2I IR3IIVRbigRsmallIsmallIbig-V sameacross both R'sI2I3I1I1junction
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