No, a light bulb is not a linear resistor.
Light bulbs, particularly incandescent bulbs, exhibit a non-linear relationship between voltage and current due to the temperature dependence of their resistance. This means that the resistance of a light bulb changes as it heats up, which is directly related to the current flowing through it.
Why Light Bulbs Aren't Linear Resistors:
- Temperature Dependence: The filament of a light bulb is made of a material, typically tungsten, whose resistance increases significantly with temperature.
- Ohm's Law Deviation: Ohm's Law (V = IR) describes a linear relationship between voltage (V), current (I), and resistance (R). In a linear resistor, R remains constant regardless of V or I. With a light bulb, as the voltage increases, the current increases, but the resistance also increases. This leads to a non-linear relationship between voltage and current.
Explanation of the Non-Linearity:
- Initial State: When the light bulb is first turned on, the filament is at room temperature, and its resistance is relatively low.
- Heating Up: As current flows through the filament, it heats up due to the power dissipated (P = I²R).
- Resistance Increase: As the temperature increases, the resistance of the tungsten filament also increases.
- Non-Linear Behavior: This increased resistance limits the current flow more than a linear resistor would. The relationship between voltage and current becomes curved rather than a straight line.
Linear vs. Non-Linear Resistors:
| Feature | Linear Resistor | Light Bulb (Incandescent) |
|---|---|---|
| Resistance | Constant, independent of temperature and current | Varies significantly with temperature and current |
| Ohm's Law | Follows Ohm's Law (V = IR) linearly | Deviates from Ohm's Law due to temperature |
| Voltage/Current Graph | Straight line through the origin | Curved line |
In Summary:
A light bulb's resistance changes with temperature, meaning it does not follow the linear voltage-current relationship defined by Ohm's Law for a linear resistor. Therefore, a light bulb is a non-linear resistor.
