Capacitor charging: The capacitor voltage rises exponentially toward the source voltage.
Neon threshold: The neon lamp turns on after the capacitor reaches the breakdown threshold.
Discharging: Once the neon lamp conducts, the capacitor voltage drops and the lamp turns off.
Effect of R: Increasing resistance increases τ, making the blinking slower.
Effect of C: Increasing capacitance also increases τ, so it takes longer to charge and discharge.
Model note: This simulation uses a simplified threshold model to emphasize the physics idea of RC charging, discharging, and neon-lamp switching.
RC Circuit Physics Simulation: Neon Lamp Flasher
This interactive physics simulation demonstrates an RC circuit connected to a neon lamp. Students can adjust the resistance and capacitance to see how the time constant controls capacitor charging, discharging, and the blinking behavior of the neon lamp.
Physics Model
In an RC circuit, the time constant determines how quickly the capacitor voltage changes. A larger resistor or capacitor produces a larger time constant and a slower voltage response.
τ = RC
Charging: VC(t) = V0(1 − e−t/RC)
Discharging: VC(t) = V0e−t/RC
How the Neon Lamp Flashes
The neon lamp acts like a voltage-threshold device. At first, the capacitor charges through the resistor. When the capacitor voltage reaches the lamp’s breakdown threshold, the neon lamp turns on and the capacitor discharges through the lamp. When the voltage drops below the sustaining level, the lamp turns off and the capacitor begins charging again.
What Students Learn
How resistance and capacitance determine the time constant τ = RC.
Why capacitor voltage changes exponentially instead of linearly.
How a threshold device such as a neon lamp can produce blinking behavior.
How circuit simulations can connect mathematical equations to visual behavior.