5 Ohm Resistor: Color Code & Power Applications Guide

Working on power electronics and audio circuits, I’ve found the 5 ohm resistor shows up more often than you’d expect. It’s not your typical signal-level component. This is a power resistor value, commonly found in dummy loads, amplifier testing setups, and current limiting applications where you need to dissipate real watts without generating excessive voltage drops.

This guide covers the 5 ohm resistor color code for accurate identification, power rating selection, and the real-world applications where this specific value earns its keep on the test bench.

Understanding the 5 Ohm Resistor

A 5 ohm resistor provides exactly 5 ohms of electrical resistance. This relatively low value places it firmly in power electronics territory. At 5Ω, the component passes significant current at modest voltages, making power dissipation the primary design concern.

One important detail engineers should know: 5 ohm is not part of the standard E24 resistor series, which includes nearby values like 4.7Ω and 5.1Ω. However, 5.0Ω appears in the E48 and E96 precision series, and manufacturers produce it widely due to its practical utility in power applications. You’ll find 5 ohm resistors readily available from all major distributors.

Key Specifications for 5 Ohm Resistors

Specification	Typical Values
Resistance	5Ω (nominal)
Standard Series	E48, E96 (precision)
Tolerance Options	±0.1%, ±0.5%, ±1%, ±2%, ±5%
Power Ratings	1W, 2W, 3W, 5W, 10W, 25W, 50W, 100W+
Temperature Coefficient	20-250 ppm/°C
RKM Code Notation	5R0
Package Types	Axial, chassis mount, SMD, wirewound, aluminum-clad

5 Ohm Resistor Color Code Explained

Identifying the 5 ohm resistor color code requires understanding that values under 10 ohms use the Gold multiplier band (×0.1). The Green first band is your key identifier for any resistor starting with the digit 5.

4-Band 5 Ohm Resistor Color Code

The standard 4-band configuration uses:

Band Position	Color	Meaning
1st Band (First Digit)	Green	5
2nd Band (Second Digit)	Black	0
3rd Band (Multiplier)	Gold	×0.1
4th Band (Tolerance)	Gold	±5%

Calculation: 5 + 0 = 50 × 0.1 = 5Ω ±5%

The Green-Black-Gold-Gold sequence is distinctive. Both Gold bands serve different functions: the third band multiplies by 0.1, while the fourth indicates ±5% tolerance.

5-Band 5 Ohm Resistor Color Code (Precision)

For precision applications, 5-band resistors add a third significant digit:

Band Position	Color	Meaning
1st Band	Green	5
2nd Band	Black	0
3rd Band	Black	0
4th Band (Multiplier)	Silver	×0.01
5th Band (Tolerance)	Brown	±1%

Calculation: 5 + 0 + 0 = 500 × 0.01 = 5Ω ±1%

6-Band 5 Ohm Resistor Color Code

For temperature-critical power applications:

Band	Color Sequence	Meaning
Bands 1-5	Green-Black-Black-Silver-Gold	5Ω ±5%
6th Band (TCR)	Black	250 ppm/K

Multiplier Reference for Low-Ohm Values

Multiplier Color	Value	Example Result
Black	×1	50 × 1 = 50Ω
Gold	×0.1	50 × 0.1 = 5Ω
Silver	×0.01	500 × 0.01 = 5Ω

Complete Color Code Reference Chart

Color	Digit Value	Multiplier	Tolerance
Black	0	×1	–
Brown	1	×10	±1%
Red	2	×100	±2%
Orange	3	×1,000	–
Yellow	4	×10,000	–
Green	5	×100,000	±0.5%
Blue	6	×1,000,000	±0.25%
Violet	7	–	±0.1%
Gray	8	–	±0.05%
White	9	–	–
Gold	–	×0.1	±5%
Silver	–	×0.01	±10%

Types of 5 Ohm Power Resistors

Selecting the right 5 ohm resistor type depends heavily on your power requirements and whether inductance matters for your application.

Wirewound 5 Ohm Resistors

Best for: High-power dissipation, dummy loads, DC applications

Specification	Typical Value
Power Rating	5W to 500W+
Tolerance	±1% to ±5%
TCR	20-80 ppm/°C
Inductance	Present (not suitable for RF)

Wirewound resistors handle the most power per dollar. The trade-off is inductance from the wound wire element, which matters at higher frequencies. For audio testing and DC applications, wirewound is often the economical choice.

Non-Inductive 5 Ohm Resistors

Best for: RF dummy loads, audio amplifier testing, high-frequency applications

Specification	Typical Value
Power Rating	10W to 250W
Tolerance	±1% to ±5%
Construction	Carbon composition, thick film, or bifilar wound
Frequency Range	DC to 3 GHz (depending on construction)

Non-inductive resistors maintain flat impedance across frequency, critical for accurate amplifier measurements and RF applications.

Aluminum-Clad (Chassis Mount) Resistors

Best for: High-power applications requiring heatsinking

Specification	Typical Value
Power Rating	25W to 100W+ (with heatsink)
Mounting	TO-247, TO-220, or bolt-down
Thermal Resistance	1-3°C/W (to heatsink)

Aluminum-clad resistors transfer heat efficiently to external heatsinks. The rated wattage typically assumes proper thermal management.

SMD Power Resistors

For PCB-mounted power applications:

Package Size	Power Rating	Max Current (5Ω)
1206	1/4W	224mA
2010	3/4W	387mA
2512	1W	447mA
2725	2W	632mA
Custom	5W+	1A+

Power Applications for 5 Ohm Resistors

Dummy Loads for Amplifier Testing

The most common application for a 5 ohm resistor in my workshop is amplifier dummy loads. When testing audio amplifiers, you need a resistive load that simulates speaker impedance without producing sound.

A 5Ω load works well for testing amplifiers designed for 4Ω speakers (providing a conservative margin) or creating combination loads. Many engineers build configurable dummy loads using 5Ω resistors:

Configuration	Total Resistance	Power Capacity
Single 5Ω	5Ω	Resistor rating
Two 5Ω in series	10Ω	Sum of ratings
Two 5Ω in parallel	2.5Ω	Sum of ratings
5Ω + 3Ω in series	8Ω	Limited by lower rating

Power Supply Load Testing

Testing power supply regulation requires known load resistors. A 5Ω resistor draws predictable currents:

Supply Voltage	Current Draw	Power Dissipated
5V	1A	5W
12V	2.4A	28.8W
24V	4.8A	115.2W
48V	9.6A	460.8W

These calculations show why power rating selection is critical. A 12V/5Ω test already requires a 50W minimum resistor with proper derating.

Speaker Impedance Matching

Adding a 5 ohm resistor in series with a speaker increases total impedance. This technique matches lower-impedance speakers to amplifiers requiring higher loads:

Speaker Impedance	With 5Ω Series	New Total
3Ω	+ 5Ω	8Ω
4Ω	+ 5Ω	9Ω
8Ω	+ 5Ω	13Ω

Note that series resistance reduces power delivered to the speaker and may affect frequency response.

Current Limiting Applications

Low-value resistors like 5Ω serve as current limiters in charging circuits, motor soft-start applications, and inrush current protection:

Voltage	Current Limit	Power Required
5V	1A	5W
12V	2.4A	28.8W
24V	4.8A	115.2W

Power Dissipation Calculations for 5 Ohm Resistors

Proper power rating selection prevents resistor failure and potential fire hazards.

Power Calculation Formulas

For a 5Ω resistor:

P = I² × R simplifies to P = I² × 5

P = V²/R simplifies to P = V²/5

Power Requirements by Current Level

Current	Power Dissipated	Minimum Rating (2× safety)
100mA	0.05W	1/4W
500mA	1.25W	3W
1A	5W	10W
2A	20W	50W
5A	125W	250W
10A	500W	1000W

Always apply at least a 2× derating factor for continuous operation. For intermittent duty, you can sometimes operate closer to rated power with adequate cooling.

Thermal Considerations

Cooling Method	Typical Power Increase
Free air	Baseline rating
Forced air (fan)	1.5-2× rating
Heatsink mounting	2-4× rating
Oil immersion	3-5× rating
Water cooling	5-10× rating

Many DIY dummy load builders use oil immersion (transformer oil or mineral oil) to dramatically increase power handling of inexpensive resistors.

Selecting the Right 5 Ohm Resistor

Selection Decision Matrix

Application	Recommended Type	Key Considerations
DC power supply testing	Wirewound, chassis mount	Power rating, heatsinking
Audio amplifier testing	Non-inductive	Flat frequency response
RF dummy load	Non-inductive	SWR, frequency range
Current limiting	Metal oxide, wirewound	Pulse rating, surge capability
PCB mount	SMD thick film	Power density, thermal design

Tolerance Impact on 5 Ohm Resistors

Tolerance	Actual Range	Best Applications
±0.1%	4.995Ω to 5.005Ω	Precision measurement
±1%	4.95Ω to 5.05Ω	Audio testing, calibration
±5%	4.75Ω to 5.25Ω	General power applications
±10%	4.5Ω to 5.5Ω	Non-critical loads

Useful Resources and Databases

Online Calculators

• DigiKey Resistor Color Code Calculator: https://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-resistor-color-code
• All About Circuits Calculator: https://www.allaboutcircuits.com/tools/resistor-color-code-calculator/
• Calculator.net Resistor Tools: https://www.calculator.net/resistor-calculator.html

Component Distributors

• DigiKey: https://www.digikey.com
• Mouser Electronics: https://www.mouser.com
• Newark/Farnell: https://www.newark.com
• Surplus Sales of Nebraska: https://www.surplussales.com (power resistors)
• Parts Express: https://www.parts-express.com (audio load resistors)

Resistor Manufacturers

• Ohmite: High-power wirewound and chassis mount
• Vishay/Dale: Precision power resistors
• Caddock: Non-inductive power film resistors
• TE Connectivity: Industrial power resistors
• Arcol: Aluminum-clad power resistors

Frequently Asked Questions

What is the color code for a 5 ohm resistor?

A 4-band 5 ohm resistor uses the color code Green-Black-Gold-Gold. Green represents 5, Black represents 0, the first Gold band is the ×0.1 multiplier, and the second Gold indicates ±5% tolerance. For precision 5-band versions with ±1% tolerance, the code is Green-Black-Black-Silver-Brown.

Is 5 ohm a standard resistor value?

While 5 ohm is not in the basic E24 series (which includes 4.7Ω and 5.1Ω), it appears in the E48 and E96 precision series. More importantly, manufacturers produce 5Ω power resistors widely because of practical demand for dummy loads and testing applications. You’ll have no trouble sourcing this value.

What power rating do I need for a 5 ohm resistor?

Calculate power using P = I² × 5 or P = V²/5. For 1A current through 5Ω, power is 5W. Always apply at least a 2× safety factor, so use a 10W minimum resistor. For 2A, power is 20W, requiring at least a 50W resistor. Include thermal management (heatsinking or airflow) for sustained high-power operation.

Can I use a 5 ohm resistor as a speaker dummy load?

Yes, a 5 ohm resistor works well as a dummy load for amplifier testing. It’s close enough to standard 4Ω or 8Ω speaker impedances for most testing purposes. For audio applications, use non-inductive types (not wirewound) to maintain flat frequency response. Ensure adequate power handling, as even a 100W amplifier can destroy an undersized resistor instantly.

Why does my 5 ohm resistor get hot during use?

Heat is the natural byproduct of power dissipation in resistors. At 5Ω, even moderate currents generate significant heat: 2A produces 20W of heat continuously. If your resistor is too hot to touch, it may be undersized for the application. Either increase the resistor’s power rating, add heatsinking, improve airflow, or reduce the current/duty cycle.

Summary

The 5 ohm resistor is a workhorse component in power electronics and testing applications. While not part of the basic E24 series, its practical utility in dummy loads, amplifier testing, and current limiting ensures wide availability across power ratings from 1W to hundreds of watts.

Remember the color code: Green-Black-Gold identifies a 5Ω value before checking the tolerance band. For power applications, always calculate actual dissipation and apply appropriate safety margins. When building dummy loads, consider whether your application requires non-inductive construction for accurate high-frequency measurements.

Whether you’re testing a guitar amplifier, loading a power supply, or building a calibration fixture, proper selection of power rating and resistor type will ensure reliable, safe operation.