This circuit demonstrates and compares how the three fundamental passive elements—a resistor, a capacitor, and an inductor—respond to identical square-wave voltage pulses.
Circuit Overview
The design consists of three parallel, independent sub-circuits driven synchronously by matched 1 kHz pulse generators (#V1, #V2, and #V3), each outputting a 0 V to 1 V square wave:
Resistive Branch (#R1):
Driven by source #V1, resistor #R1 () exhibits purely ohmic behavior.
The current through #R1 instantaneously follows the voltage profile according to Ohm's law:
There is no phase shift or energy storage; the current steps instantaneously to during each pulse.
Capacitive Branch (#C1):
Driven directly by source #V2, capacitor #C1 () demonstrates the derivative relationship of capacitive current:
During the flat portions of the pulse where , zero current flows. During the rising and falling edges, sharp current spikes appear as charge is forced into and out of the dielectric.
Inductive Branch (#L1):
Driven by source #V3 through a small series resistance #R2 (), inductor #L1 () illustrates inductive inertia:
When the voltage pulse is applied, the inductor opposes an instantaneous jump in current, producing a ramp-up in current and an exponential transient governed by time constant:
Oscilloscope Traces
Blue: Current through resistor #R1.
Green: Voltage at node #vR (the pulse input).
Orange: Current through capacitor #C1, highlighting the edge-triggered displacement spikes.
Red: Voltage across inductor #L1 at node #vL.
