Resistor and resistance calculation with color code

Resistor and Resistance Calculation with Color Code

A resistor is an electrical component that limits or regulates the flow of electrical current in an electronic circuit. Resistors can also be used to provide a specific voltage for an active device such as a transistor.

All other factors being equal, in a direct-current (DC) circuit, the current through a resistor is inversely proportional to its resistance, and directly proportional to the voltage across it. This is the well-known Ohm's Law. In alternating-current (AC) circuits, this rule also applies as long as the resistor does not contain inductance or capacitance.

Resistors have standard colors for identification of the resistance value. In order, the colors are: black, brown, red, orange, yellow, green, blue, violet, gray, and white. Reading resistors is a very simple procedure if you use the chart and formula below.

Hold the resistor with the gold or silver band to the right and read the resistor from the left to the right.

Resistance = (1st Digit x 10 + 2nd Digit) x Multiplier

Example: This resistor, read from left to right, has the colored bands of RED, VIOLET, YELLOW, SILVER.

Using the formula and chart above, the resistance would be:

R = 1st Digit x 10 + 2nd Digit) x Multiplier
R = (RED X 10 + VIOLET) x YELLOW
R = (2 x 10 + 7) x 10,000
R = 27 x 10,000
R = 270,000 ohm (270 K ohms)

Since the final band is silver, the tolerance is 10%.