1 Answer
The term **dynamic resistor** typically refers to the resistance of a component or material that changes in response to an applied voltage, current, or other external factors like temperature or light. Unlike a static resistor, whose resistance value is constant, a dynamic resistor’s resistance can vary.
In general, there isn't a single "formula" for a dynamic resistor because its resistance depends on the specific device or material. However, for certain devices like **varistors** or **thermistors**, the relationship between resistance and some external condition (like voltage or temperature) can be expressed mathematically.
1. **Thermistor (Temperature-Dependent Resistor)**:
- For a **NTC thermistor** (Negative Temperature Coefficient), the resistance decreases as the temperature increases:
\[
R(T) = R_0 e^{\frac{B}{T}}
\]
where:
- \( R(T) \) is the resistance at temperature \( T \),
- \( R_0 \) is the resistance at a reference temperature,
- \( B \) is a constant related to the material,
- \( T \) is the absolute temperature in Kelvin.
2. **Varistor (Voltage-Dependent Resistor)**:
- For a **varistor**, the resistance is voltage-dependent and often follows a power law:
\[
R(V) = \frac{V}{I}
\]
where:
- \( R(V) \) is the resistance at voltage \( V \),
- \( I \) is the current,
- \( V \) is the applied voltage.
Alternatively, the resistance of a varistor can be described as:
\[
R(V) = k V^{-n}
\]
where \( k \) and \( n \) are constants specific to the varistor.
In short, the formula for a dynamic resistor depends on the specific device or material and how it responds to external factors.
In general, there isn't a single "formula" for a dynamic resistor because its resistance depends on the specific device or material. However, for certain devices like **varistors** or **thermistors**, the relationship between resistance and some external condition (like voltage or temperature) can be expressed mathematically.
1. **Thermistor (Temperature-Dependent Resistor)**:
- For a **NTC thermistor** (Negative Temperature Coefficient), the resistance decreases as the temperature increases:
\[
R(T) = R_0 e^{\frac{B}{T}}
\]
where:
- \( R(T) \) is the resistance at temperature \( T \),
- \( R_0 \) is the resistance at a reference temperature,
- \( B \) is a constant related to the material,
- \( T \) is the absolute temperature in Kelvin.
2. **Varistor (Voltage-Dependent Resistor)**:
- For a **varistor**, the resistance is voltage-dependent and often follows a power law:
\[
R(V) = \frac{V}{I}
\]
where:
- \( R(V) \) is the resistance at voltage \( V \),
- \( I \) is the current,
- \( V \) is the applied voltage.
Alternatively, the resistance of a varistor can be described as:
\[
R(V) = k V^{-n}
\]
where \( k \) and \( n \) are constants specific to the varistor.
In short, the formula for a dynamic resistor depends on the specific device or material and how it responds to external factors.