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

The phasor diagram is a name given to a sketch in the complex plane of the phasor voltages and currents throughout a specific circuit

8-2 Superposition, source transformation and Thevenin's theorem Superposition:

8-1 Nodal, mesh and loop analysis Nodal analysis:

We define the ratio of the phasor voltage to the phasor current as impedance

《电路》（英文版）7-6 Phasor relationships for、and R:

sinusoidal current or voltage at a given frequency is characterized by only two parameters an amplitude and a phase angle. The complex representation of the voltage or current is also characterized by these same two parameters