SG_Chap18

# SG_Chap18 - Energy Try it Example Calculate current through each resistor R 1 = 10 R 2 = 20 R 3 = 30 V b =44 V Complex circuits For HW very tricky

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1 Chapter 18 Direct-Current Circuits • DC: current goes only in one direction –Most intuitive, similar to water flow –The baby of Thomas Edison 18.1 Sources of EMF Most common: batteries, generators (voltage) ( Historically they are called sources of electromotive force (EMF)) The terminal voltage is ΔV = V b -V a ΔV = ε – Ir For the entire circuit, ε = IR + Ir 18.2 Resistors in Series R R = 2R 18.3 Resistors in Parallel R R = R/ 2 Example

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2 18.4 Kirchhoff’s Rules Junction Rule – The sum of the currents entering any junction must equal the sum of the currents leaving that junction • A statement of Conservation of Charge Loop Rule – The sum of the potential differences across all the elements around any closed circuit loop must be zero • A statement of Conservation of
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Unformatted text preview: Energy Try it! Example: Calculate current through each resistor. R 1 = 10 , R 2 = 20 , R 3 = 30 , V b =44 V Complex circuits For HW: very tricky when finding the power or current for a given resistor R 1 R 2 R 3 V b 18.5 RC Circuits • C circuits – Charging is done "instantly"; q = CV – Not good; can ruin the battery – Add some resistance to slow it down • RC Circuits Example: (a) How long does it take the charge on the capacitor to drop to one-fourth of its original value (in multiples of )? (b) If V= 12V, R = 2 and C = 3.5 F, find the initial charge on the capacitor and the time it takes to discharge? 3 18.6 Household circuits and 18.7 electrical safety...
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## This note was uploaded on 03/30/2009 for the course PHY 102 taught by Professor Luo during the Spring '08 term at SUNY Buffalo.

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SG_Chap18 - Energy Try it Example Calculate current through each resistor R 1 = 10 R 2 = 20 R 3 = 30 V b =44 V Complex circuits For HW very tricky

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