Do you know your resistors?

A resistor is a two terminal component that resists the flow of current. They are a passive component i.e they can only consume power and not generate it. Usually they are used to limit the current flowing through other components. For example If we connect a Light emitting diode (LED), to a battery it would burn outrightly because the battery would allow a large amount of current to flow through the LED, this can be avoided if we put a resistor between the LED and the battery. We can calculate the resistance of a resistor using the Ohm’s law V=IR. Usually we calculate the resistance by reading the color bands of the resistor or by measuring it with a multimeter. Each strip of color on the resistor represents a specific digit. Different colors corresponding to their digit values are shown in the image below




a’ represents the 1st significant digit, which is the first band color of resistor.

b’ represents the 2nd significant digit, which is the second band color of resistor.

c’ represents the 3rd significant digit, which is the third band color of resistor.

d’ represents the 4th significant digit, which is the fourth band color of resistor and this is the multiplier value used in formula.

e’ represents the 5th significant digit, which is the fifth band color of resistor and this is the tolerance value of resistor.


Let’s take an example of a 5-band resistor with the colors brown, green, red, black and gold, according to the formula the resistance will be: 152 * 1 = 152 Ohms with 5% tolerance. In the case of a resistor with four colour bands the third band color gives the multiplier value and the fourth band color represents the tolerance value of the resistor.