Understanding Resistors: Types, Features, and Applications

Posted on Sep 1, 2025 in Electromechanical Engineering

RESISTORS: Components that oppose the current.

Types: Linear, Nonlinear, Variable.
LINEAR RESISTORS FIXED:
Features:
1. Nominal Resistance (RN): Expected value in ohms of resistance at 25ºC.
2. Tolerance: Difference between the upper and lower resistance values.
3. Power Rating (PN): Maximum continuous power the component can dissipate without deteriorating.
4. Maximum Voltage (Vmax): Maximum AC voltage (50Hz) or DC voltage the component can withstand at a specified working temperature.
5. Series Critical Resistance (CR): Ratio of the power rating to the rated voltage.
6. Temperature Coefficient (T): Relative change in resistance with temperature variation.

7. Voltage Coefficient (V): Variation of resistance with applied voltage.


8. Noise Voltage (Noise Index): Unwanted signal mixed with the desirable signal.

9. Behavioral Frequency: Unwanted parasitic L and C elements that ideally should be zero.
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Variable Resistor (3 Terminals): Features a movable contact called a cursor. Types include Potentiometers (voltage variation) and Rheostats (current variation), depending on load connection.
Features:
1. Laws of Change: Functions connecting resistance between fixed terminals (b1) and cursor position (b3).
§ Linear Law: Resistance = K * Adjustment + B, where K is a constant and B is the route.

§ Logarithmic Law:
§ Inverted Logarithmic Law:
2. Compliance: Degree of approximation of the real law to the theoretical law.
3. Resolution Resistance: Minimum change in resistance detectable by moving the cursor.

4. Resolution Voltage: Minimum voltage change for a detectable resistance variation.

5. Resolution Continuous Layer Resistors:
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NONLINEAR RESISTORS: Devices with a non-linear current-voltage relationship.
Types:
1. Thermistor: NTC (Negative Temperature Coefficient) or PTC (Positive Temperature Coefficient), dependent on temperature.
2. Varistors (VDR): Voltage Dependent Resistors, used for voltage stabilization and transient suppression.
3. Photoresistors (LDR): Light Dependent Resistors, resistance varies with light intensity.
4. Magnetoresistors: Resistance varies with the surrounding electric field.
5. Magnetic Bands: Resistance varies with applied pressure.
Þ IMPEDANCE: Resistance: ; Coil: ; Capacitor:
Þ REACTANCE: Resistance: ; Coil: ; Capacitor:
Þ Load Line, Operating Point (Q):

To draw the load line:
If I = 0, V = Vp
If V = 0, I = Vp / R

The point Q is the operating point.

Characteristics of ELECTRONIC COMPONENTS:
Þ Electronic Elements: Perform a simple physical function in an electric circuit when used correctly. They play roles as:
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• Active: Capable of control functions, power amplification, or more complex operations (e.g., Transistors, tubes, integrated circuits).
• Passive: Do not perform control or amplification functions; they perform basic electronic functions (e.g., resistors, capacitors, coils, diodes, thermistors, varistors).
• Transducers

Þ Common Features:

• Value: Specified by the manufacturer, associated with a tolerance indicating the maximum deviation from the nominal value. This tolerance depends on material variability and manufacturing processes.
• Stability: Property determining how component parameters change over time and with usage.
• Temperature Coefficient: Indicates the relative change of a component’s parameter (N) with temperature, defined as: . Temperature is a crucial parameter as it can alter device operation and characteristics; higher temperatures generally lead to worse performance.
• Voltage Coefficient: Similar to the temperature coefficient but related to voltage: .
• Power Rating or Maximum (Pmax): Important as it relates to temperature. It’s the maximum power an electronic component can dissipate under normal conditions when the ambient temperature does not exceed the specified temperature (Ts).
  
  
  
• Max. Working Voltage (Vmax): The highest voltage that can be applied without exceeding the rated power or breakdown voltage.
• Reliability: A feature ensuring the component’s smooth functioning.