Download Resistor Code and Tolerance Guide

Resistor Color Code: for first two digits reading from left to right (in a 4-band type) or for
first 3 digits (in a 5-band type)
0 = blk
1 = brown
2 = red
3 = orange
4 = yellow
5 = green
6 =blue
7 =violet
8 = grey/gray
9 = white
3rd band from the left is the “multiplier”, n, specifying the value of the exponent of 10^n that gets
multiplied by the first two (or 3) digits of the resistor to find its rated value of resistance (in units of
ohms)
4th band is the tolerance specifying plus-or-minus 5%(if gold) and plus-or-minus 10% (if silver) for a 4band resistor. Five band resistors offer tighter tolerances like 1%(brown) or 2%(red) as indicated by
their last band.
Summary of reading resistor color codes:
1st band= first digit
2nd band= 2nd digit
3rd band=multiplier
4th band=tolerance
5% = gold
10% = silver
20% = no color
Example: Reading from left to right
brown blk red gold
1 2 x10^2 +/-5% = 1200+/-5%
= 1200+/-60 ohms
range: Min of 1200-60 to Max of 1200+60
(1140 to 1260 ohms)
Sample Assessment as first used in past Spring 2013 (may be under
continuous revision):
Students are assigned to read pages 8-23 and page 62 of the EMT1130
Lab manual covering safety and how color coding can be used to
determine the resistance of any given four-band resistor.
Short answer assessment questions: (students are to give their responses in their own words?-assessed
based on how well they understand the general concepts for each question as expressed in the answer)
1. List at least three things you should do if/when there is an electrical fire in your home?
Answer choices: Call for help/phone 911; Turn off the power sourcing the fire; Use a Cat./Class C fire
extinguisher or try to smother the fire with non-flammable material.
2. List at least three things you should do if/when there is an electrical fire in your lab/work area?
3. What is the color code of a resistor that is 220 ohms with 5% tolerance?
Answer: Red, red, brown, gold
4. Which is the meaning of the following color code combinations is of greater resistance value?
Put a checkmark on the correct answer:
(1) yellow, violet, red, silver
(2) blue, orange, brown, gold
5. What should you do if a resistor connected to a "live" circuit appears to be abnormally hot(burning)?
Answer: Immediately turn off power to the circuit and try to find where the problem lies(why the
resistor overheated)
6.List what symptoms or signs indicate an electrical shock? What should you do if someone appears to
have been shocked by electricity?