... from the GND pin of Arduino to the GND rail of the bread-board. Connect the GND rail of the breadboard to the EMITTER pin of the transistor (Figure 2-4).2. Connect the BASE pin of the transistor ... metal, making it morereactive with atmospheric gases. As the various gases react with the metal, the resistance changes in proportion to the amount of that gas present in the air exposed to the ... Constant widthUsed for program listings, as well as within paragraphs to refer to pro-gram elements such as variable or function names, databases, datatypes, environment variables, statements,...