Demo Number 022
Location Shelf 33
Description A piece of graphite is attached as a resistor load to a power supply and current is passed through the graphite until it glows and ultimately flashes.
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  • Detailed instructions in the box.
  • You will need:
    • DC Power supply on shelf 61(must supply at least 6A).
    • Mechanical Pencil “Lead” (Graphite).
    • 2 banana-alligator clips.
    • Lab stand.
  • Initially, the resistance is about an ohm but as the current through the graphite heats it up, some of the graphite burns away. As this happens the cross-sectional area gets smaller increasing the resistance. Increased resistance dissipates more heat and eventually, the graphite glows (as seen in the picture). Once the graphite gets narrow enough the heat burns through it. Just before this happens there is a very intense flash.

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This Demo is Part of the following Categories: 5D20 Resistivity and Temperature