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PHYSICS-PLAYDOH LAB

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Abstract

Resistanceand resistivity can be demonstrated using simple modeling materialslike the play-doh. This experiment is a simple practicaldemonstration of how resistivity can be obtained in a laboratory setup using a play-doh resistor. Resistivity depends on length and areaand this are worked in the experiment. Resistance and resistivity inthis case are linear functions and the resultant graph drawn willgive a constant for resistivity.

Physics-playdoh lab

Resistanceand resistivity describe the extent to which an object or materialimpedes the flow of electric current [ CITATION Fus13 l 1033 ]. The purpose of this report is to look at resistivity of play-doh atdifferent lengths. It is also important to note that the resistanceof an object depends on its shape and the material used in moldingthe object. In this case the shape of the play-doh is cylindrical.

Whena current is passed through a conductor and a resistor, theresistance of the material can be determined by Ohms law that is V =IR

WhereV= voltage, I= current and R = resistance.

Inorder to determine resistivity of the material and in this case theplay-doh, the length and the cross sectional area must be worked out. The relationship between resistance and resistivity is given by R= ρ (L/A)

Whereρ is resistivity, L = length of the play-doh and A = the crosssectional area of the play-doh. The relationship is a linear one ofthe form y = mx + c hence the gradient of the linear graph obtainedby plotting R against L/A will give us a constant value which will beequivalent to resistivity of the play-doh.

Methods

Inthis experiment the play doh was modeled in a cylindrical manner andthe length was 0.1m. The play doh is then connected to an ammeterand a voltmeter and a power source as indicated in the diagram below

Thefollowing equipment will be required:

Ammeter,terminals, voltmeter, modeling clay,

Thediameter of the play-doh was varied so as to give different valuesfor the cross sectional area. The current flowing through the playdoh and voltage were recorded using the ammeter and voltmeterrespectively.

Results

Table1 below shows the results obtained in the experiment

Table1.

diameter of play-doh -d (m) |
radius of play-doh -r (m) |
cross sectional area -A (m^2) |
current (I) |
voltage (V) |
resistance -R |
Length/area L/A |

0.04 |
0.02 |
0.001257 |
0.1 |
1 |
10 |
79.55449 |

0.035 |
0.0175 |
0.000963 |
0.113 |
1.15 |
10.17699 |
103.8422 |

0.03 |
0.015 |
0.000707 |
0.106 |
1.26 |
11.88679 |
141.4427 |

0.025 |
0.0125 |
0.000491 |
0.9 |
1.34 |
1.488889 |
203.666 |

0.02 |
0.01 |
0.000314 |
0.037 |
1.55 |
41.89189 |
318.4713 |

0.015 |
0.0075 |
0.000177 |
0.052 |
1.7 |
32.69231 |
564.9718 |

0.01 |
0.005 |
0.000079 |
0.025 |
2.21 |
88.4 |
1265.823 |

Lrepresents the length of the circular play-doh (0.1m), while Arepresents the cross sectional area of the play-doh.

Figure1: Graph of resistance of the play-doh against L/A

Discussion

Giventhat Resistance (R) is directly proportional to the ratio of lengthof the play-doh (L) to its cross sectional area (A), then resistivityof the play-doh is given by the slope or gradient of the line in thegraph in figure 1 above. In this case resistivity is 2.378 which isobtained from a regression of R and L/A.

Thecolor of the material for the play doh does not affect resistivity inthis case and hence color does not make any difference in theresults.

Conclusion

Theresults obtained in this experiment supported by the graph drawnclearly indicate that resistivity depends on resistance as a functionof the ratio of length of material used in the play-doh to the crosssectional area. This is easily applied in cases where the play-dohis cylindrical.

References

Fuse, Christopher and Etal. "Resistivity in play-doh." __THE PHYSICS TEACHER__ (2013): 351.