ABSTRACT
An ideal resistor is an electronic component, the fundamental feature of which is resistance R according to Ohm’s law expressed by the equation
V ¼ RI (11:1)
where V represents voltage in volts I is the current in amperes R is the resistance in ohms
The main parameters of a resistor are nominal resistance value, nominal power dissipation, and limited voltage value. According to their construction and technology, we can divide resistors into five groups: wirewound resistors, foil resistors, thin film resistors, thick film resistors, and bulk resistors. Each group has some advantages and disadvantages; until now it has been impossible to manufacture all of the needed resistors within one technology. It is more interesting to divide resistors with respect to their application into two groups as follows:
1. Fixed resistors, including low-power resistors of 0.05-2 W, high-power resistors of 2-100 W, highvoltage resistors, high-ohmic resistors, chip resistors, resistive networks
2. Variable resistors (potentiometers), including rotary control potentiometers, slide control potentiometers, preset potentiometers, and special potentiometers
11.1.1.2 Fixed Resistor
An ideal fixed resistor is an electronic component, the resistance value of which is constant with time and different environmental conditions. In practice, we can observe some changes of resistance in time and under high temperature, high humidity, frequency, and electrical load conditions, and so on. Those changes of a resistance, called the instability of resistor, are the basis for classification of resistors according to the requirements of the International Electrical Commission (IEC) and the International Organization for Standardization (ISO 9000-9004) in order to build in a reliability system. Figure 11.1 presents different kinds of fixed resistors. Each resistor is marked mainly by resistance
value R and production tolerance dp(). Nominal resistance is rated according to the E6, E12, E24, E48, and E96 series. It is very important for the user to know not only the production deviation dp but also dynamic tolerance D.
