The resistor is one of the fundamental building blocks of the electrical circuit. Just about every electrical device ever manufactured contains at least one of them. They divide voltages, they limit current, they protect sensitive components and, along with capacitors and transistors, they help us to design just about every current imaginable. Look in the RS Components catalogue and you’ll find thousands of different types of resistor. But for the most part they come in two types: fixed and variable. These are used in different ways in different applications.…