将下列英文翻译为中文 How to monitor the brightness of a light in a circuit? Which segment decides the brightness of the light in the circuit, as shown in  Fig  2-1  ? We can see the brightness adjustable light anywhere in the market or in our home. Rotate the knob, the light will turn brilliant or turn dark. So when you rotate the knob, what has changed in the circuit?  All electrical circuits fall into one of three classes: series circuits, parallel circuits, and series parallel circuits.  A series circuit is one in which the current flows in a single continous path and is of the same value at every point in circuit (Fig2-2).  In a parallel circuit there are two or more current paths between two points in the circuit, as shown in Fig 2-3.Here the current divides at A, one part going through R1, and the other part through R2, and combines at B to return to the battery.