An RLC circuit is set up with a light bulb in series with a variable inductor and capacitor. As the inductance or capacitance is adjusted, the circuit reaches resonance at a specific frequency, where the inductive reactance and capacitive reactance cancel each other out. At resonance, the impedance of the circuit is minimized, allowing maximum current to flow, causing the light bulb to glow brightly. This demonstrates the concept of resonance in an RLC circuit and its effect on circuit current.