A resistor is one of the most fundamental components in electronics. It silently ensures the safe and stable operation of all kinds of equipment we use daily. From regulating current, voltage division to protecting sensitive components, resistors play crucial roles in the field of electronics. So, what is a resistor?
In simple terms, a resistor is a component used to control the magnitude of current, adjust signal levels, divide voltage, and protect other components. The resistor symbol is usually presented as a zigzag or rectangular shape in circuit diagrams (depending on regional standards). Different types of resistors have different characteristics, applications and structures.
In this article, we will provide a comprehensive introduction to different types of resistors, including their characteristics and application fields. We will also introduce and explain how to identify resistance values through color ring codes. After reading this article, you are sure to gain knowledge about the selection methods of resistor types and the skills for identifying color rings.
Overview of Types of Resistors
Resistors can be classified into various types according to different standards. The main classification methods are as follows:
1. Based on Behavior
Resistors can be classified according to their working characteristics into linear resistors and nonlinear resistors.
Linear Resistors refer to the type of resistors whose resistance values remain constant, such as metal film resistors, carbon film resistors, etc. This resistor type follows Ohm's law (V=IR), where the current is directly proportional to the voltage across it. This means that regardless of how the voltage applied across the resistor changes, the resistance value of the resistor itself will not change with external conditions such as voltage or current.
The resistance value of nonlinear resistors is not constant. They are types of resistors that undergo significant changes with variations in external environmental conditions, such as temperature, voltage, light, magnetic field, etc. This type of resistor does not follow Ohm's law, meaning that there is no simple direct proportion between its current and voltage.
2. Based on Construction
Resistors can be classified according to their structure and adjustability into fixed resistors and variable resistors.
The resistance value of a fixed resistor is not adjustable. This type of resistor is commonly found in the most fundamental applications in circuits, such as current limiting, voltage division, and load handling. Its representative types include carbon synthetic resistors, metal film resistors, wound resistors, surface mount resistors (SMD), etc.
Variable resistors can adjust their resistance values as needed, such as potentiometers, rheostats, trimmers, etc. This type of resistor is widely used for volume regulation, brightness adjustment and circuit calibration.
3. Based on Usage
Resistors can be classified according to their application fields into general-purpose resistors and special-purpose resistors.
General-purpose resistors are often used in common scenarios such as basic current limiting, voltage division and protection, offering high cost performance and a wide variety of types.
Special-purpose resistors are designed for specific functions, such as thermistors (for temperature detection), varistors (for surge protection), and photoresistors (for light control circuits), etc.
The above mainly classifies resistors from three aspects. To sum up, different types of resistors have their own unique structures and performances.
Types of Resistors
In the following content, we will introduce in depth each major resistor type, including linear resistors, variable resistors, and nonlinear or special resistors. By understanding the characteristics, advantages and common applications of these different types of resistors, you will be able to select the most suitable components for specific electronic projects.
Linear Resistors
Linear resistors can be further classified into fixed resistors (with unchangeable resistance values) and variable resistors (with adjustable resistance values).
Fixed Resistors
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Resistor Type
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Definition
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Characteristics
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Advantages
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Common Applications
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Carbon Composition Resistor
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Made by compressing carbon powder and binder into a solid cylinder.
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High noise, low stability, obsolete today
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Handles short overloads, low cost
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Old radios, power supplies, replaced in modern use
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Carbon Film Resistor
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Carbon film deposited on a ceramic core.
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Stable, moderate precision
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Low noise, good temp. stability
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General-purpose electronics, common fixed resistor
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Metal Film Resistor
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Thin layer of metal (e.g., nickel-chromium) on a ceramic rod.
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High precision, low noise
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Excellent accuracy, low temp. coefficient
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Audio, instrumentation, precision circuits
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Metal Oxide Film Resistor
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Metal oxide film applied to a ceramic substrate.
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Good surge and heat resistance
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Stable in harsh conditions
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Industrial controls, power supplies
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Wire-Wound Resistor
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Resistive wire wound around an insulating core.
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High power rating, accurate
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Handles large currents, robust
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Power amplifiers, motor drives, load banks
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Thick/Thin Film Resistor
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Thick or thin resistive film deposited on a substrate.
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Thin film: high precision; thick: cheap
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Versatile for SMD/precision circuits
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SMD electronics, hybrid circuits
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Surface Mount Resistor (SMD)
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Compact resistor designed for surface-mount technology.
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Small size, leadless
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Saves space, automated assembly
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Phones, computers, modern electronics
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Foil Resistor
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Uses ultra-thin metal foil as the resistive element.
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Ultra-low temp. coefficient, very stable
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Highest precision, long-term reliability
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Precision measurement, aerospace
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Network/Array Resistor
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Multiple resistors integrated into a single package.
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Multiple values, single package
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Saves PCB space, consistent values
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Memory modules, logic boards, signal termination
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Film Type Resistor
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General term for resistors using a resistive film (carbon/metal/oxide).
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Versatile in type and value
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Good performance, mass production
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Universal in all electronics
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Ohmic Resistor
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Any resistor that obeys Ohm's Law (linear V-I relationship).
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Linear and predictable
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Easy calculation, reliable
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All basic electronic and electrical circuits
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Variable Resistors
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Resistor Type
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Definition
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Characteristics
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Advantages
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Common Applications
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Potentiometer
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A three-terminal variable resistor used as an adjustable voltage divider.
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Adjustable via rotation/slider
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Easy control, versatile
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Volume, brightness control
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Rheostat
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Two-terminal variable resistor mainly used for current adjustment.
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Designed for higher currents
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Robust, smooth adjustment
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Motor speed, heater adjustment
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Trimmer Resistor
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Miniature variable resistor for fine circuit calibration.
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Set once, small size
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Precise, space-saving
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Tuning, offset/frequency adjustment
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Nonlinear / Special Types of Resistor
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Resistor Type
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Definition
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Characteristics
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Advantages
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Common Applications
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Thermistor (NTC/PTC)
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Resistance varies sharply with temperature; NTC decreases, PTC increases with temp.
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Temp.-sensitive
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Inexpensive, quick
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Temp. sensors, overcurrent/overheat protection
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Varistor
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Resistance drops rapidly above a voltage threshold for surge protection.
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Voltage-dependent
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Absorbs surges
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Surge protectors, power strips
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Photoresistor (LDR)
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Resistance decreases as light intensity increases.
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Light-dependent
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Simple, passive
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Auto lighting, light meters, alarms
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Magneto-Resistor
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Resistance changes in response to magnetic field strength.
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Magnetic field-sensitive
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Non-contact detection
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Speed sensors, compasses
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Humistor
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Resistance varies with ambient humidity.
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Humidity-sensitive
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Direct measurement
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Air conditioning, weather stations
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Force Sensitive Resistor (FSR)
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Resistance decreases with applied force or pressure.
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Force/pressure-sensitive
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Thin, flexible
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Electronic scales, robotics, smart insoles
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How to choose different types of resistors?
When choosing the appropriate types of resistors for electronic design, multiple key parameters need to be comprehensively considered. Here are some of our suggestions:
1. Reference Power Rating
The power rating refers to the maximum power that a resistor can safely consume without being damaged. If the actual power consumption exceeds the rated value, the resistor will be damaged due to overheating. When choosing the type of resistor, a resistor type with a power rating at least twice the actual demand should be selected to ensure safety. If the circuit needs to withstand large currents or high voltage drops, high-power types such as wire-wound resistors can be given priority.
2. Look at the Temperature Coefficient
The temperature coefficient indicates the extent to which the resistance value changes with temperature. Generally, the lower the temperature coefficient, the more stable the resistance value of the resistor in different environments. Therefore, for high-precision analog or measurement circuits, we should choose high-stability resistor types such as metal film resistors or foil resistors with extremely low temperature coefficients.
3. Tolerance
Tolerance refers to the allowable deviation between the actual resistance value of a resistor and its nominal resistance value. Different types of resistors correspond to different tolerance levels. For instance, metal film resistors can achieve extremely low tolerances (as low as ±0.1%), while the tolerances of common carbon film resistors may be larger (±5% or ±10%). So we should select the type of resistor with an appropriate tolerance based on the precision requirements of the circuit.
After selecting the appropriate resistor type based on key parameters such as power, temperature coefficient, and tolerance, accurately identifying and confirming the resistance value of the resistor is equally crucial.
Resistor Color Code Calculation
The resistor color code is an internationally common standard coding system. It is used to concisely represent the resistance value, tolerance and sometimes the temperature coefficient of a fixed resistor. Mastering the reading and calculation methods of the resistance color ring can ensure that we make correct selections when assembling circuits and replacing various types of resistors.
So how to read the color ring of a resistor?
Common resistor types are mostly marked with 4-color rings, 5-color rings or 6-color rings. Each color band represents a specific number, magnification or parameter according to the International color ring chart:
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Color
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Digit
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Multiplier
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Tolerance
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Black
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0
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×1
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|
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Brown
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1
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×10
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±1%
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Red
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2
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×100
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±2%
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Orange
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3
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×1,000
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|
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Yellow
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4
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×10,000
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|
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Green
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5
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×100,000
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±0.5%
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Blue
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6
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×1,000,000
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±0.25%
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Violet
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7
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×10,000,000
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±0.1%
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Gray
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8
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×100,000,000
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±0.05%
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White
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9
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|
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Gold
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×0.1
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±5%
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Silver
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×0.01
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±10%
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None
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|
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±20%
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The first ring of a 4-color ring resistor is the first significant figure. The second ring is the second significant figure. The third ring is the multiplier and the fourth ring is tolerance.
For example：
10K resistor
The first three rings of a 5-color ring resistor are the first, second and third significant figures, the fourth ring is the multiplier, and the fifth ring is the tolerance.
The 6-color ring resistor is the same as the 5-color ring one, but its 6th ring indicates the temperature coefficient (ppm/°C).
Note：
When reading the color wheel, start from the end close to the color band (tolerance color bands are usually gold, silver or have a larger interval).
For critical applications or resistors with unclear color rings, it is recommended to use a multimeter to reconfirm.
Conclusion
Understanding different types of resistors is essential for all electronic-related personnel. Each type of resistor - whether linear, variable or nonlinear - has its unique performance and advantages. After reading this article, you can confidently choose the most suitable type of resistor. In addition, one can also master the identification and calculation of the resistor color code, and quickly and accurately determine the resistance value. Here are several articles that can help you consolidate and enhance the resistor color code calculation: 10K resistor, 1.2K resistor, 100 ohm resistor.
In conclusion, a solid grasp of the types of resistors and the knowledge of color ring identification can help us design, build and maintain high-performance and highly reliable electronic circuits more efficiently.
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