What is a Resistor?
A resistor is a fundamental electrical component used to control or limit the flow of electric current within an electronic circuit. In addition to current regulation, resistors are often employed to set a specific voltage level required by active components like transistors.
In a direct current (DC) circuit, the behavior of a resistor is governed by Ohm’s Law, which states that the current through a resistor is inversely proportional to its resistance and directly proportional to the voltage across it. This principle also holds true in alternating current (AC) circuits, provided the resistor does not introduce inductive or capacitive effects.
Types of Resistors
Resistors come in various types and are manufactured using different materials and techniques:
- Carbon-Composition Resistors
These are among the most common types used in electronic devices. They are made by mixing finely ground carbon (graphite) with a clay binder, then hardening the mixture. The resistance value is determined by the carbon-to-clay ratio—the higher the carbon content, the lower the resistance. - Wirewound Resistors
Made by winding a resistive wire, typically Nichrome, around an insulating core, wirewound resistors can handle higher currents compared to carbon-composition resistors of the same size. However, due to their coil-like construction, they also exhibit inductance. While this has no effect in DC circuits, it can impact performance in AC circuits by making the resistor frequency-dependent.