Extended Surface - Lab Report Example

tions, V and I are directly proportional to each other, and therefore R and G are constant (although they can depend on other factors like temperature or strain). This proportionality is called Ohms law, and materials that satisfy it are called "Ohmic" materials. In other cases, such as a diode or battery, V and I are not directly proportional, or in other words the I–V curve is not a straight line through the origin, and Ohms law does not hold. In this case, resistance and conductance are less useful concepts, and more difficult to define.

The ratio V/I is sometimes still useful, and is referred to as a "chordal resistance" or "static resistance", as it corresponds to the inverse slope of a chord between the origin and an I–V curve. In other situations, the derivative dV/dI may be most useful; this is called the "differential