A Resistor is an electronic component that resists the flow of electricity, typically to maintain a current that is safe for other electrical components being used later in the circuit. Resistance itself is measured in ohms, after Georg Simon Ohm of Ohm’s Law. Ohm’s Law dictates how a resistor will behave, as is written as I=V/R where I is the current, V is the voltage, and R is the resistance. The values of resistors are marked on them using colored stripes, which can be “decoded” to identify the resistor.
Before reading the resistor, it is important that it be oriented in the right direction. Place the resistor so that the side with stripes closest to the edge is on the left. In most cases, this will mean that the right-most stripe is gold or silver.
To begin reading the color bands on a resistor, it will help to memorize this mnemonic: Bad Boys Ravish Only Young Girls But Violet Gives Willingly. This will make is easy to remember the values associated with each color, as the colors are black, brown, red, orange, yellow, green, blue, violet, gray, and white, in that order. Now, assign a number to each color, starting with 0 so that black = 0, brown = 1, red = 2, etc.
Now, to actually read the resistor, start with the left-most strip. Identify the number correlated with the first stripe and write it down. Do the same for the next stripe as well.
The third strip is the multiplier value, which essentially tells us how many zeros to add to our number so far. For the multiplier strip, you will need to know two additional colors: gold and silver. Gold is .1 and silver is .01, meaning that a gold band would indicate that the decimal should be moved one space to the left, and silver means that the decimal should be moved two space to the left. In addition to gold and silver, all of the other colors are used as well. Aside from gold and silver, the third band will indicate how many zeros to add to your number.
The final strip is the quality stripe, essentially indicating the standard deviation from the resistor’s value in a percentage. The fourth strip will either be silver which is +/- 10%, gold which is +/- 5%, red which is +/- 2%, or brown which is +/- 1%.
As an example, a resistor with strips in this order: brown, red, yellow, and gold would have 120000 o hms (more commonly written as 120 k ohms). Factoring in the quality stripe, this resistor will have a value of 120 k ohms +/- 5%.