Series Resistor Lamp Dimmer

Application

This circuit uses a series resistor to reduce current through the Light Bulb, similar to a simple low-brightness indicator or current-limited load. It is configured as an interactive operating point demo so resistor changes update the table and bulb brightness immediately.

Design Context

The series resistor and lamp form a simple voltage divider. Increasing R1 lowers lamp voltage and lamp current, which demonstrates the tradeoff between supply voltage, current limiting, and visible load brightness.

Expected Behavior

With R1 set to 120 ohm and LAMP1 set to 120 ohm, the 12 V source divides roughly evenly between the resistor and lamp. The table should show about 6 V at the lamp node and about 50 mA of lamp current. Reducing R1 raises lamp current and brightness; increasing R1 lowers both.

Key Values

• Simulation mode: interactive operating point
• Supply: 12 V DC
• Series resistor: 120 ohm
• Lamp resistance: 120 ohm
• Expected starting current: about 50 mA

Suggested Experiments

• Change R1 to 47 ohm, 120 ohm, and 330 ohm and compare lamp current.
• Compare lamp voltage against the 12 V supply voltage.
• Change LAMP1 resistance to model a different indicator load.

Featured Component

The Light Bulb is the measured load. Its dynamic symbol is driven by simulated current, so the schematic provides a quick visual cue while the table gives the numeric operating point.