2002 AAPT Apparatus Competition, Boise State University
Name: P.
J. Ouseph
Address: Physics
Department
University of Louisville
Louisville, KY 40292
Phone: 502 852 0918
Fax: 502
852 0742
E-mail: pjouse01@louisville.edu
Apparatus Title: Square Carbon
Paper Resistors
Abstract (40-50 words)
Five square resistors are made using conducting carbon paper with electrodes drawn on them. A multimeter is used to measure the resistance of the resistors. All these resistors have equal resistance, that is, resistance of a square resistor is independent of its width and length.
Equipment
required to construct apparatus:
Item Source/Store Part Number Cost
1. 2 sheets of carbon paper, Pasco PK 9026 $ 1.00
2. Conductive ink pen, Pasco PK 9031B $ 17.00
3. Digital Multimeter, Pasco SE-9786 $ 41.00
Total cost $ 59.00
Description
Squares of 1 in, 2 in, 3 in, 4
in and 5 in sides are cut from conducting carbon paper purchased from Pasco and
electrodes are drawn on them with conducting ink pen (available from Pasco). A
multimeter is used to measure their resistances. It is interesting for the
students to observe that all resistors, independent of their size, are of equal
resistance. Explaining this result is
found to be educational, especially in teaching the resistance equation, R = rl/A.
Cross sectional area of the carbon paper resistor, A = t x w, where t is the
thickness of the paper and w, its width. Since the resistor is square its width
is equal to length. Therefore, R = r/t. That is the resistance of the square
resistor is independent of its dimensions.