where
I is the current through the
conductor in units of
amperes,
V is the potential difference measured across the conductor in units of
volts, and
R is the resistance of the conductor in units of
ohms.
The ratio of the voltage applied across a resistor's terminals to the intensity of current in the circuit is called its resistance, and this can be assumed to be a constant (independent of the voltage) for ordinary resistors working within their ratings.
The electrical functionality of a resistor is specified by its resistance: common commercial resistors are manufactured over a range of more than nine
orders of magnitude. When specifying that resistance in an electronic design, the required precision of the resistance may require attention to the
manufacturing tolerance of the chosen resistor, according to its specific application. The
temperature coefficient of the resistance may also be of concern in some precision applications. Practical resistors are also specified as having a maximum
power rating which must exceed the anticipated power dissipation of that resistor in a particular circuit: this is mainly of concern in power electronics applications. Resistors with higher power ratings are physically larger and may require
heat sinks. In a high-voltage circuit, attention must sometimes be paid to the rated maximum working voltage of the resistor.
Practical resistors have a series
inductance and a small parallel
capacitance; these specifications can be important in high-frequency applications. In a
low-noise amplifier or
pre-amp, the
noise characteristics of a resistor may be an issue. The unwanted inductance, excess noise, and temperature coefficient are mainly dependent on the technology used in manufacturing the resistor. They are not normally specified individually for a particular family of resistors manufactured using a particular technology.
[1] A family of discrete resistors is also characterized according to its form factor, that is, the size of the device and the position of its leads (or terminals) which is relevant in the practical manufacturing of circuits using them.
Axial-lead resistors on tape. The tape is removed during assembly before the leads are formed and the part is inserted into the board. In automated assembly the leads are cut and formed.
Title : Resistor
Description : A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. The curr...
