Page 1 of 3 PHYS1120 Exam II review Things to remember for PHYS1110 algebra trig sin cos vector math especially vector addition Fnet ma problems free body diagrams Exam I Material E fields Gauss s Law Chapter 23 Voltage Electric Potential Definition of voltage V Uof q q f E dr U of q q V i dV V E x if E constant and E x E x dx E hi V lo V Voltage is electrical height E field is slope if r E V 0 equipotential lines Voltage due to a point charge Q V r kQ r Voltage due to many charges V r Vi i i k Qi ri k dq r Work done by external agent to move charge q through a voltage difference V Wext U of q q V If charge q falls through a voltage difference V KE PE q V Units of electron volts eV Ch 24 Capacitors Q V V E d Q capacitance C Q V 10 11 2009 M Dubson PHYS1120 Notes University of Colorado at Boulder Page 2 of 3 C depends only on size and shape C A d o area A d Adding capacitors in series and parallel 1 QV 2 stored energy U U volume energy per volume u 1 Q2 2 C 1 C V2 2 1 2 oE 2 Ch 25 26 Current and Circuits I dQ dt J E J 1 E Ohm s Law V I n q vd A where n carriers volume vd drift speed resistivity measure of internal friction depends on composition I R where R constant I lo V hi V R V Resistance of a resistor R power P L A area A L W V2 I V I2 R t R Equivalent Resistance R1 in series R2 Rtot R1 R2 R tot R1 in parallel R2 10 11 2009 M Dubson PHYS1120 Notes 1 1 1 R1 R2 University of Colorado at Boulder Page 3 of 3 Things that are always true in circuits elements in series always have the same current I I I I Rbig R1 R2 R3 V Ismall Rsmall elements in parallel always have the same voltage Ibig V same across both R s voltage change along an unbroken ideal wire is zero since we assume R wire 0 Vwire I R wire I 0 0 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 of I2 I1 I1 junction I1 I 2 I3 junction I3 junction K s Voltage Law Loop Law total voltage change around any closed loop is zero Ammeters and Voltmeters To 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 Boulder
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