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PHASE CHANGE IN IRON WIRE

PHASE CHANGE IN IRON WIRE

PHASE CHANGE IN IRON WIRE
Demo Number 082
Location Shelf 9
Description The iron wire is strung horizontally above the lecture table. If we heat the wire by passing an electric current through it the wire will expand and sag. If the heating power is turned off the wire will cool to room temperature in an approximately exponential manner according to Newton’s law of cooling.
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Tips
  • The wire used in this demonstration is 22 gauge (0.064 cm diameter) “Black Annealed” iron wire which is sold in hardware stores for general utility use. The wire is strung horizontally above the lecture table with only a little sag when it is cold and it is connected to a variable transformer VARIAC on shelf  61 (set Voltage at Low and make it 35 Volts for 1.5 m wire).
  • Be careful with Voltage, wire can burn easily!
  • DO NOT PLUG INTO WALL!!!!

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This Demo is Part of the following Categories: 5D20 Resistivity and Temperature, 4C45 Phase Changes: Solid-Solid

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