Resistors are one of the simplest varieties of electronic components. A resistor is a two-terminal device that has a fixed relationship between the current passing through the device and the voltage drop across the device.
This relationship is described in Ohm’s law, which states that “the strength of a direct current is directly proportional to the potential difference and inversely proportional to the resistance of the circuit” (Merriam-Webster).
This relationship is illustrated by the following equation:
I = current in amps (A)
V = voltage in volts (V)
R = resistance in ohms (Ω)
Although resistors are very common and simple devices, the different composition types of resistors are often misunderstood.
There are three common resistor composition types:
Carbon resistors are the most common type of composition resistors. They are inexpensive, and serve a general purpose in electronic circuits.
Carbon Film Resistors
A film resistor uses a film of carbon that is deposited (either sprayed or coated) onto a substrate, which forms the resistive element. The resistance is adjusted by cutting or shaping the film.