5D20.20-Wire coil in Flame

Video: Watch this demo

Description: This demonstration shows how a wires electrical resistance changes with temperature.


  • 2V Lightbulb
  • Thin Wire Coils
  • DC Power Supply
  • Propane Blowtorch


  1. Connect the circuit as shown above; the lightbulb, coil, and DC power supply should be in series
  2. Turn the voltage on the power supply to 2V
  3. With the propane torch, heat the coil just until the coil becomes red; the light should dim
  4. Turn off the power supply when finished


  • Avoid overheating the coil; the coils are fragile and will break if the flame is on them for too long
  • If more coils are needed, 32 gauge wire works best