Variable Inductor
PARTS AND MATERIALS
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Paper tube, from a toilet-paper roll
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Bar of iron or steel, large enough to
almost fill diameter of paper tube
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28 gauge "magnet" wire
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Low-voltage AC power supply
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Incandescent lamp, rated for power supply
voltage
CROSS-REFERENCES
Lessons In Electric Circuits, Volume
1, chapter 14: "Magnetism and Electromagnetism"
Lessons In Electric Circuits, Volume
1, chapter 15: "Inductors"
Lessons In Electric Circuits, Volume
2, chapter 3: "Reactance and Impedance -- Inductive"
LEARNING OBJECTIVES
SCHEMATIC DIAGRAM
ILLUSTRATION
INSTRUCTIONS
Wrap hundreds of turns of magnet wire around
the paper tube. Connect this home-made inductor in series
with an AC power supply and lamp to form a circuit. When the
tube is empty, the lamp should glow brightly. When the steel
bar is inserted in the tube, the lamp dims from increased
inductance (L) and consequently increased inductive
reactance (XL).
Try using bars of different materials, such
as copper and stainless steel, if available. Not all metals
have the same effect, due to differences in magnetic
permeability. |