A simple series RLC circuit with a voltage source Vs.

RLC Circuit Model with Function Generator

The RLC Circuit with Function Generator model simulates a resistor R, a capacitor C, and an inductor L in series with either a sinusoidal or a square wave source voltage Vs(t) and plots the time dependence of the voltage drops across the source, the resistor, and the capacitor. The differential equation for the charge on the capacitor Q can be found by applying Kirchhoff's loop rule.

Because we are solving a dynamical model, transients are observed when the program is run.  The resistance, capacitance, inductance and source frequency can also be varied at runtime.

1. Run the model and observe what happens as you change the frequency, inductance (L), resistance (R) and capacitance (C). The plot shows the source voltage (gray) as well as the voltages across each circuit element (color coded to the the input boxes at the top of the window).
2. Pick a specific point in time and measure each of the voltages and verify that the voltage across the inductor (red), resistor (green) plus capacitor (blue) do indeed equal the value of the source voltage (gray).
3. Consider the square wave simulation.  Describe what happens to the voltage across each element when the voltage source switches.  Explain why that happens.
4. Now run the simulation with a sinusoidal voltage source. The resonant frequency of this circuit is given by ω_o=(LC)^-1/2.  where  ω=2πf. Change the frequency to the resonant frequency.  Pick different values of L and C and observe what happens at the new resonant frequency. Specifically, how does the resistor voltage compare with the source voltage? Explain.