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BASIC NEC 2023

Resistor Color Code & Resistor Fundamentals Practice Test

Free online resistor color code practice test. 25 basic electrical questions on reading 4-band and 5-band resistor color codes, tolerance bands, resistor types, and power ratings. Good for electrician exam prep.

TOPICS COVERED

Resistor Basics Color Code Basics Color Code Digits Color Code Reading Tolerance Bands 5-Band Resistors

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Resistors are the most common component in electronics, and reading their color code is a core skill. Each colored band on a resistor represents a digit, a multiplier, or a tolerance. A standard 4-band resistor has two significant-digit bands, a multiplier band, and a tolerance band. Learn the color-to-number sequence (black=0, brown=1, red=2, orange=3, yellow=4, green=5, blue=6, violet=7, gray=8, white=9) and you can read any resistor value at a glance, without a meter.

25

Questions

38 min

Time

75%

Pass

Timer starts immediately. Progress is auto-saved.

Resistor Color Code & Resistor Fundamentals Practice Test — Question List

Question 1: What is the basic function of a resistor in a circuit?

To oppose or limit the flow of current
To store electrical energy for later use
To generate voltage on its own
To convert AC to DC

Question 2: Resistance is measured in which unit?

Ohms
Watts
Farads
Henrys

Question 3: On a standard 4-band resistor, what do the first two bands represent?

The two significant digits of the resistance value
The power rating of the resistor
The tolerance of the resistor
The multiplier only

Question 4: In the resistor color code, the color black represents the digit:

0
1
9
10

Question 5: In the resistor color code, the color brown represents the digit:

0
1
2
7

Question 6: In the resistor color code, the color red represents the digit:

2
3
5
8

Question 7: A resistor has the color bands Brown-Black-Red-Gold. What is its resistance value and tolerance?

100 ohms +/-5%
1,000 ohms +/-5%
10,000 ohms +/-5%
1,000 ohms +/-10%

Question 8: A resistor has the color bands Yellow-Violet-Orange (no 4th band). What is its resistance value?

4,700 ohms
47,000 ohms
470,000 ohms
47 ohms

Question 9: A resistor has the color bands Red-Red-Brown. What is its resistance value?

22 ohms
220 ohms
2,200 ohms
2.2 ohms

Question 10: A gold tolerance band on a resistor indicates a tolerance of:

+/-1%
+/-5%
+/-10%
+/-20%

Question 11: A silver tolerance band on a resistor indicates a tolerance of:

+/-2%
+/-5%
+/-10%
+/-20%

Question 12: If a resistor has no 4th (tolerance) band at all, what tolerance is assumed?

+/-1%
+/-5%
+/-10%
+/-20%

Question 13: How does a 5-band resistor color code differ from a 4-band code?

It uses three significant digit bands instead of two, for higher precision
It has no tolerance band at all
It is only used for variable resistors
It has a lower maximum power rating

Question 14: A "fixed" resistor is one that:

Has a single, set resistance value that cannot be adjusted
Can be adjusted by turning a knob or shaft
Only works in AC circuits
Has no resistance at all

Question 15: A potentiometer is a variable resistor that:

Has three terminals and is commonly used to create an adjustable voltage divider
Has only one terminal
Cannot be adjusted once installed
Only works with AC power

Question 16: A rheostat is a variable resistor typically used to:

Limit or adjust the current flowing in a circuit
Store energy like a battery
Convert AC to DC
Measure voltage directly

Question 17: Which of the following is a common standard power rating for a small general-purpose resistor?

1/4 watt
100 watts
1000 watts
1 megawatt

Question 18: If a resistor is forced to dissipate more power than its rated wattage, what typically happens?

It overheats and can burn out or fail
Nothing happens, resistors have no power limit
The resistance value automatically decreases to compensate
It converts into a capacitor

Question 19: Carbon composition resistors, compared to modern metal film resistors, generally have:

Wider tolerance and more electrical noise
Tighter tolerance and less noise
No tolerance rating at all
Infinite power rating

Question 20: Metal film resistors are popular in modern circuits mainly because they offer:

Tighter tolerance and better stability than carbon composition types
The lowest possible cost of any resistor type
The highest power rating of any resistor type
No color code at all

Question 21: Wirewound resistors are typically chosen for applications that require:

High power dissipation
Extremely small physical size only
Zero resistance applications
Use only in low-voltage signal circuits

Question 22: A surface-mount resistor is printed with the code "472." What is its resistance value?

472 ohms
4,700 ohms
47,000 ohms
47 ohms

Question 23: A surface-mount resistor is printed with the code "103." What is its resistance value?

103 ohms
1,300 ohms
10,000 ohms
100,000 ohms

Question 24: A resistor's "temperature coefficient" describes:

How much its resistance value changes as its temperature changes
How hot the resistor can get before it explodes
The color of the resistor body
How much current it can conduct at absolute zero

Question 25: A 1,000 Ω resistor marked with a ±5% tolerance band means its actual resistance could measure anywhere between:

999 ohms and 1,001 ohms
950 ohms and 1,050 ohms
900 ohms and 1,100 ohms
800 ohms and 1,200 ohms

EXAM CARD BASIC

Questions25

Time limit38 min

Pass score75%

Code editionNEC 2023

DifficultyIntermediate

Last reviewedJun 2026

Timer starts immediately. Progress is auto-saved.

Source: NEC 2026 (NFPA 70)