The most fundamental of these ideas are probably the notions of electrical potential, resistance, and current. Given a particular voltage level across the terminal parts of a circuit and a certain level of resistance within it, a set amount of current resistor will flow. That simple relationship lies at the heart of just about every circuit design, even if certain kinds of components and layouts can introduce quite a bit of complexity. In practice, dealing with these very basic and important ideas will account for quite a bit of what any circuit designer of any level of commitment and skill will focus on over time.
As a result, the selection of resistors for particular circuits likewise tends to be extremely important, as well. In many cases, resistors of the least expensive and most widely available kinds will be perfectly sufficient, with billions of film-style or wire-wound resistors being turned out by manufacturers, as a result, each and every year. In others, however, more imposing requirements will mean that resistors of less usual sorts will instead have to be selected and employed.
In many situations, for example, circuits where high voltage and relatively low internal resistance are the norm will turn out to be the only way of accomplishing a certain task. When that is the case, current resistor that are rated to handle wattage levels a great deal higher than usual will be needed. These power resistors tend to be designed using technologies entirely different from the norms at the low end of the scale, with a great deal of thought going into their construction, as well.
A high power resistor will also often be designed to be able to dissipate heat more efficiently, so that its performance and longevity do not degrade as the temperature rises too high. Whether by selecting a resistor of this kind or precision resistors that are manufactured to much tighter tolerances, there are therefore good ways of building on the basics of electronic circuit design with more specialized choices.