Bulb (Incandescent)
An incandescent lamp that produces visible light by heating a tungsten filament. Resistance increases with temperature, creating a non-linear V–I characteristic. A classic load for demonstrating Ohm's law and thermal effects.
Properties
| Property | Description | Default | Range |
|---|---|---|---|
| Rated voltage | Voltage at which the bulb operates at rated power (V) | 12 V | 1.5 V – 240 V |
| Rated power | Power dissipation at rated voltage (W) | 10 W | 0.5 W – 1 000 W |
| Resistance model | How filament resistance varies with temperature (Constant / Thermal) | Thermal | — |
Simulation behavior
At rated voltage the bulb glows at full brightness. Below rated voltage it glows dimmer; above it glows brighter but approaches failure.
With the Thermal resistance model, cold resistance is approximately 1/10 of the hot resistance — the bulb draws a large inrush current at switch-on that drops as the filament heats up. With the Constant model, resistance is fixed at V²_rated / P_rated.
If power dissipation significantly exceeds the rated value, the filament burns out (fails open) and the bulb goes dark.
Tips
- The inrush current with the Thermal model can be 5–10× the steady-state current — size your fuse or transistor switch accordingly.
- Lower the supply voltage below the rated value to observe dimming — the bulb's resistance also decreases slightly, drawing proportionally less current than a pure resistor would.
- Replace the bulb with an LED in your design to eliminate the thermal non-linearity and reduce power consumption.