What is a Resistor? A resistor is an electronic component which produces a voltage across its terminals that is proportional to the electric current passing through it; this is in accordance with Ohm's law:
Where the voltage V is the result of multiplying the current I by the resistance R; this equation can be transposed to obtain anyone of the three values. The three interchangeable Ohm's law expressions are:
As an example, if the voltage V is 12 volts and resistance R is 400 ohms, a current I of 12 / 400 = 0.03 amperes will flow through the resistance R. The unit of electrical resistance is an ohm; the sybol for this is a large omega Ω. The common sub multiple of the ohm is the milliohm (1x10^-3) and the multiples the kilohm (1x10^3) and megaohm (1x10^6). Practical resistors can be made of various compounds and films, as well as resistance wire. Resistors are elements of electronic circuits and electrical networks and are found almost everywhere in most electronic equipment. The primary characteristics of a resistor are the resistance, power rating, the maximum working voltage and the tolerance. Other characteristics of a resistor are its noise, temperature coefficient, inductance and the lesser known critical resistance. Resistors may be integrated into printed circuits, hybrid circuits and integrated circuits. The position of leads and size of resistors are relevant to equipment designers. This is because resistors must be large enough (physically) as to not overheat when dissipating their power. |
