# SCEN103 Play-Doh Exercise

### Resistivity and Play-Doh

Objective:
Measure dependence of resistance on diameter of resistor

Hypothesis
Anyone?

Procedure

• Roll as many of the following cylinder diameters as material and time permits:

Sample   Diameter   Circumference
cm cm
1 0.8 2.5
2 0.9 2.8
3 1.0 3.1
4 1.1 3.5
5 1.3 4.1
6 1.6 5.0
7 2.0 6.3

Cover the full range; that is, make cylinders numbers 7, 5, 3, and then 1. Fill in the intermediate values next. Make each cylinder about 12 in long; it will be necessary to measure the larger cylinders before fabricating the smaller ones.

• The quality of the experimental results will depend strongly on the uniformity of the cylinders.
• Same diameter over the entire length
• No cracks or voids, knead thoroughly before rolling
• After the cylinders are completed, bring to the front of the classroom for measurement in the circuit shown:
• Record voltage across 10 cm of material.
• Record current through cylinder.
• The two measurements above should be made simultaneously!
• For each cylinder:
• Calculate its resistance using Ohm's Law.
• Calculate its cross-sectional area.
• On the markerboard, report:
• Color of Play-Doh sample and names of participants.
• Diameter (in cm), Area (in sq. cm), and resistance (in ohm) of each cylinder.
• Graph the results to test your hypothesis.

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