What is a Resistor ?
A passive electrical component with two terminals that are used for either limiting or regulating the flow of electric current in electrical circuits.
A resistor is the simplest implementation of Ohm’s law.
The law says the current flowing through a material is directly proportional to voltage applied across that material and the proportionality constant is the resistance of the material at a constant temperature.
Which is the classic formula we are all familiar with, where V is the voltage in Volts, I is the current in Amps and R is the resistance.
In terms of electronics, the resistor reduces electrical current by a precise amount. If you consider that in a circuit you typically have a fixed input voltage, and resistors offer a fixed amount of resistance, you can then use Ohm’s Law to determine how much a resistor will limit current.
The resistance of any material is dictated by four factors:
- Material property—each material will oppose the flow of current differently.
- Length— the longer the length, the more is the probability of collisions and, hence, the larger the resistance.
- Cross-sectional area—the larger the area A, the easier it becomes for electrons to flow and, hence, the lower the resistance.
- Temperature—typically, for metals, as temperature increases, the resistance increases.
Thus, the resistance R of any material with a uniform cross-sectional area A and length is directly proportional to the length and inversely proportional to its cross-sectional area in mathematical form.