Example 2: Find the three inductance appearing in the T equivalent of the transformer shown in Fig., if L2=4H and the input inductance at A-B is 6H with C-D open-circuited, and 2H with C-D short-circuited

A current i at Li produces an open circuit voltage u,at L2s dyal

Find the resonant frequency arallel resonance

Frequency characteristics(Xi, xc,x,z, y, o vs o Z=R+A=R+(L+Xc)=R+ilo I

Let us now define resonance. In a two-terminal electrical network containing at least one inductor and one capacitor, resonance is the condition which exists when the input impedance of the network is purely resistive

Example 2: (p175-12) resistor, capacitor, and voltage source=100cos300n are all in series. If the average power dissipated by the resistor is 150W and the rms capacitor voltage is 10v, determine R and C

sinusoidal voltage: V =V29 A sinusoidal current: I= We define the complex powerS=vi=V∠9,I∠-9 =V∠,-=V∠=+ jVI sin=P+j P=VIcos 9 --active(average) power

We assume=Im cos(t+a)i=Im cos(ot+B) The phase angle by which the voltage leads

Example 1: If 0=4v2 cos\tV, Z=2/600Q2 Find p(t)and P. Solution:

《电路》（英文版）9-1 Instantaneous power