Phasor diagram can only solve the simplest series circuit and the simplest parallel circuit. In order to master the principle of sinusoidal steady-state circuit completely, we must learn to write KCL equation, KVL equation and VCR relationship in complex form and learn to solve complex algebraic equations.

Drawing lines can broaden students' thinking and solve many problems skillfully. For example, the library has 150 science and technology books, and the story books are three times as many. How many story books are there than science books? The general solution is: 150× 3- 150 = 300 (Ben). But the application of line graph makes students have a simpler solution.

relevant knowledge

The general term in technical drawing refers to a continuous or discontinuous drawing line composed of one or more different line elements, such as a solid line segment or a double-point long line segment composed of "long stroke, short interval, point, short interval, point and short interval".

Connect two points with a ruler and you get a line segment. The length of a line segment is the distance between these two points. Line segments are represented by letters A and B or lowercase letters representing their two endpoints. Sometimes these letters also represent the length of the line segment, which is recorded as line segment AB or line segment BA, line segment A .. where A and B represent the two endpoints of the line segment.