This experiment contains two 100 watt light bulbs and a large inductor. The circuit diagram is set up as shown with a parallel circuit, one branch has a single bulb and the other branch has the inductor and the second bulb wired in series along that branch. When the iron core is placed inside the inductor it greatly increases the inductance and changes the AC phase of the circuit causing the bulb in line with the inductor to greatly reduce in brightness while the other bulb is unaffected.

Pira DCS # 5J20.20

Equipment
Inductor		Iron Core		Variac
Light Bulbs		Wires