AC i-V relationship for R, L, and C

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AC i-V relationship for R, L, and C Resistive Load Source v S (t) Asint t R A R v R i t A t v v R S R sin sin V R and i R are in phase or representation: v S (t) =Asint = Acos(t-90°)= A -90°=V I S (jw) =(A / R)-90° Impendence: complex number of resistance Z=V S (j)/ I S (j)=R Generalized Ohm’s law V S (j) = Z I S (j) Everything we learnt before applies for phasors with generalized ohm’s law

description

AC i-V relationship for R, L, and C. Source v S (t) = Asin w t. Resistive Load. V R and i R are in phase. Phasor representation: v S (t) =Asin w t = Acos( w t-90 ° )= A -90 °= V S (j w ). I S (j w ) =(A / R) -90 °. - PowerPoint PPT Presentation

Transcript of AC i-V relationship for R, L, and C

Page 1: AC i-V relationship for R, L, and C

AC i-V relationship for R, L, and C

Resistive Load Source vS(t) Asint

tR

A

R

vRi

tAtvv

R

SR

sin

sin

VR and iR are in phase

Phasor representation: vS(t) =Asint = Acos(t-90°)= A -90°=VS(j)

IS(jw) =(A / R)-90°

Impendence: complex number of resistance Z=VS(j)/ IS(j)=R

Generalized Ohm’s law VS(j) = Z IS(j)

Everything we learnt before applies for phasors with generalized ohm’s law

Page 2: AC i-V relationship for R, L, and C

Capacitor Load

CjCj

jj

C

j

XjI

jVZ o

CC

CC

1

90

tCAdt

dqi

Cvq

ttAv

CC

CC

C

cos

sin

90sin1

tC

AiC

ICE

VC(j)= A -90°

Notice the impedance of a capacitance decreases with increasing frequency

o

cC X

AjI 0

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Inductive Load

tL

Adt

L

Ai

dt

diLv

tAv

L

LL

L

cossin

sin

90sin tL

AiL

Phasor: VL(j-90°IL(j)=(A/L) -180°

ZL=jL

ELI

Opposite to ZC, ZL increases with frequency

Page 4: AC i-V relationship for R, L, and C

AC circuit analysis

• Effective impedance: example

• Procedure to solve a problem– Identify the sinusoidal and note the excitation frequency.

– Covert the source(s) to phasor form

– Represent each circuit element by its impedance

– Solve the resulting phasor circuit using previous learnt analysis tools

– Convert the (phasor form) answer to its time domain equivalent.

Ex. 4.16, p180