ECE 1270 Introduction to Electric Circuits 0 Lecture

ECE 1270: Introduction to Electric Circuits 0 Lecture 19: Kirchoff's Laws (Revisited) Chapter 9: Sinusoidal Steady. State Analysis Section 9. 5 ECE 1270 Introduction to Electric Circuits Suketu Naik

Phasors 1 Phasor Transform or Phasor Representation 1) A phasor is a complex number that represents the amplitude and phase of a sinusoid 2) Phasors provide a simple means of analyzing linear circuits excited by sinusoidal sources ECE 1270 Introduction to Electric Circuits Suketu Naik

Frequency Domain Representation for Inductor and Capacitor 2 Inductor Capacitor 1) A Capacitor will create -90 deg phase shift (waveform shifted by 90 deg to the right) 2) An Inductor will create +90 deg phase shift (waveform shifted 90 deg to the left) ECE 1270 Introduction to Electric Circuits Suketu Naik

Frequency Domain Representation for Inductor and Capacitor 3 Let's plot impedance of an Inductor and Capacitor Use Matlab or Graphic Calculator or Multisim or LTSpice What happens to the impedance of inductor and capacitor ECE 1270 Introduction to Electric Circuits Suketu Naik at low and high frequencies?

Example 9. 6 ECE 1270 Introduction to Electric Circuits 4 Suketu Naik

AP 9. 7 5 In Class Plot in Matlab or Multisim and look for imag(Zab)=0 ECE 1270 Introduction to Electric Circuits Suketu Naik

Problem 9. 22 6 Find Zab ECE 1270 Introduction to Electric Circuits Suketu Naik

Significance of Impedance 7 Impedance § Impedance in a circuit: either inductor or capacitor or both § Impedance, Z is a complex number in frequency domain magnitude (amplitude) & phase or real & imaginary § § § Magnitude gives us scaling factor between voltage and current Phase tells us by how many degrees voltage will lead/lag current Zero phase=zero imaginary part=no phase shift=resistive Power § When current passes through resistor, power is always absorbed or lost § When current passes through impedance, power is not necessarily lost: it is simply delayed or stored § Power is resonated: it bounces back and forth without being absorbed number ECE 1270 Introduction to Electric Circuits Suketu Naik

8 Problem 9. 24 (AC Sweep plot in Multisim) (a) Find ω (angular frequency in rad/s) at which Zab is purely resistive (b) Find the value of Zab at this frequency ECE 1270 Introduction to Electric Circuits Suketu Naik