3、 Briefly introduce the contents of Kirchhoff's law of current and voltage and write the formula. 2. Three element method of first order circuit and write the formula? 3. Three elements and formula of sinusoidal alternating current?

3、 Briefly introduce the contents of Kirchhoff's law of current and voltage and write the formula. 2. Three element method of first order circuit and write the formula? 3. Three elements and formula of sinusoidal alternating current?


1. The current flowing through the same node is 0
2. Initial value f (0 +), steady value f (∞) and time constant t
3. Amplitude, frequency and initial phase