UK EE 211 - Basic EE Definitions, Units, Conventions, and Circuit Elements

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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 Prefixespico (p) 10-12nano (n) 10-9micro () 10-6milli (m) 10-3kilo (k) 103mega (M) 106giga (G) 109tera (T) 1012Kevin D. Donohue, University of Kentucky3Basic DefinitionsElectric 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 ConventionsPositive 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 RelationshipsCurrent, charge, and timeVoltage, energy, and chargeVoltage, current, and powerPower supplied equals power absorbed for all elements in a circuit.dttdqti)()( tdxxitq )()(dqdwv pdtdwdtdqdqdwvi 21211,2ttttvidtpdtwKevin D. Donohue, University of Kentucky6Passive Sign ConventionIt 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 ProblemsA 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 SourcesIndependent 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 ExamplesFind 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 CircuitsIn 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 SourcesDependent 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 ExamplesFind 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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UK EE 211 - Basic EE Definitions, Units, Conventions, and Circuit Elements

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