The displacement current flowing internally between the capacitor plates is exactly equal to the conduction current flowing in the capacitor leads

The inductance which is equivalent to several inductance connected in series is simply the sum of the series inductance

We define the unit-step forcing function as a function which is zero for all values of argument which are less than zero and which is unity(1) for all positive values of its argument

The series combination of a resistor and capacitor has a greater practical importance than does the combination of a resistor and an inductor

The complete response=the natural response+forced response

The over-damped response---- i()= A,+A, The critically-damped response-- i(t) =e (At+A2) The under-damped- response---it)e-(b1 cos+2 sino)

In either case, leading or lagging, we say that sinusoids are out of phase () if phase angles equal they are said to be in phase(同相)

The effective value of any periodic current is equal to the value of the direct current which flowing through a resistance R, delivers the same power to r as periodic current does

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

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