Battery pack, Alligator clip leads, LED, conducting foam.
Alligator clip lead, LED, conducting foam (close-up)

 

Code Number: 5D10.25

Demo Title: Conducting Foam and Play-Doh

Condition: Excellent

Principle: Length vs. Resistance

Area of Study: Electricity & Magnetism

Equipment: 

Battery pack, Alligator clip leads, LED's, conducting foam.

Procedure: 

See also 5D10.25 in Electricity and Magnetism. 

The conducting foam is used for packing and shipping of computer chips and other kinds of chip technology so that they are protected from static electricity.  It also has a linear resistance vs. length.  

Connect the ( + ) lead of the battery to the proper leg of the LED and then place the other LED leg into the end of the foam.  By placing the other battery lead into the foam at various distances you can make the LED light brightly or dimly.  

References:

  • Christopher Fuse, Brandon August, Ashley Cannaday, Casey Barker, "Resistivity in Play-Doh: Time and Color Variations", TPT, Vol. 51, # 6, Sept. 2013, p. 351.
  • Brian Jones,  "Resistance Measurements on Play-Doh TM",  TPT, Vol. 31, # 1, p. 48, Jan. 1993.