Basic EE Definitions, Units, Conventions, and Circuit ElementsUnit PrefixesBasic DefinitionsFlow ConventionsMath Notation and RelationshipsPassive Sign ConventionExample ProblemsIndependent SourcesPower Delivered/Absorbed ExamplesPower CircuitsDependent SourcesCircuit ExamplesKevin D. Donohue, University of Kentucky1Basic EE Definitions, Units, Conventions, and Circuit ElementsVolts, Current, Energy, Power, Sign Conventions, and SourcesKevin D. Donohue, University of Kentucky2Unit Prefixespico (p) 10-12nano (n) 10-9micro () 10-6milli (m) 10-3kilo (k) 103mega (M) 106giga (G) 109tera (T) 1012Kevin D. Donohue, University of Kentucky3Basic DefinitionsElectric Circuit - an interconnection of electrical components through which charge can be moved.Current - the rate of change of charge with respect to time (coulombs per second).1 Ampere = 1 coulomb per second.1 Volt = 1 joule per coulomb = 1 newton-meter per coulomb.1 Watt = 1 Ampere-Volt = 1 joule per secondKevin D. Donohue, University of Kentucky4Flow ConventionsPositive current denotes the direction of positive charge.Describe the direction of charge in both circuits.Indicate which elements are supplying and which are absorbing energy.I1=2I2=-1ABABKevin D. Donohue, University of Kentucky5Math Notation and RelationshipsCurrent, charge, and timeVoltage, energy, and chargeVoltage, current, and powerPower supplied equals power absorbed for all elements in a circuit.dttdqti)()( tdxxitq )()(dqdwv pdtdwdtdqdqdwvi 21211,2ttttvidtpdtwKevin D. Donohue, University of Kentucky6Passive Sign ConventionIt is assumed that positive charge entering the positive terminal of an element implies power absorbed by the element.Therefore, charge leaving the positive terminal of an element implies power supplied or delivered by the element.If the words absorbed or supplied are not given with a power value, power absorbed will be assumed.IVIVKevin D. Donohue, University of Kentucky7Example ProblemsA 10 volt battery is connected to a 20 watt light bulb for 30 minutes. How much charge is lost from the battery?5 coulombs of charge pass from point A to point B at a constant rate. If 100 joules is absorbed, what is the voltage across AB?Kevin D. Donohue, University of Kentucky8 +V_+v(t)_i(t)Independent SourcesIndependent sources can deliver power in a circuit. An ideal source will have either a fixed voltage OR current independent of other elements in the circuit.Kevin D. Donohue, University of Kentucky9Power Delivered/Absorbed ExamplesFind the power absorbed in each element assuming the passive sign convention +V-I IV-V+IIVa bc da1) I = 2 A, V = 3 Va2) I= -1 A, V = 4 Vb1) I = 6 A, V = -2 Vb2) I = -2A, V = -9 Vc1) I = 7 A, V = 1 Vc2) I = -3A, V = -2Vd1) I = 1 A, V = -1 Vd2) I = -2 A, V= 6 VKevin D. Donohue, University of Kentucky10Power CircuitsIn a circuit power delivered must equal power absorbed over all elements.Find power delivered and absorbed in each element.- 6 V +21+18 V-0.5 A 21+1 V-5 V +-1 AKevin D. Donohue, University of Kentucky11Dependent SourcesDependent sources can deliver power in a circuit. The voltage or current of a dependent source depends on the current or voltage in other circuit elements.CCCSCCVSVCCSVCVSF(i1)+ H ( i1 ) -G ( v1 )+ E ( v1 ) -Kevin D. Donohue, University of Kentucky12Circuit ExamplesFind power absorbed/supplied by each element in the circuit.4i1-0.5 A+ 6 V -31+5 V-0.5 A 2i1+ 1 V -+ 11 V
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