Phys259-Labatorial07-Play-Doh-Resistors-W2017 - Phys 259 Labatorial 7 Winter 2017 University of Calgary Department of Physics and Astronomy PHYS 259

Phys259-Labatorial07-Play-Doh-Resistors-W2017 - Phys 259...

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Phys 259, Labatorial 7, Winter 2017 University of Calgary Department of Physics and Astronomy PHYS 259, Winter 2017 Labatorial 7: Electrical Resistivity of Play-Doh TM One of the most basic circuit elements is a resistor, which is a device that dissipates energy. Resistive de- vices come in all shapes and sizes as can be seen in the photo on the right, which is not surprising because there is a connection between a device’s resistance and its geometry. The two are related by an intrinsic property of the material itself called the resistivity . For instance, any two pieces of copper will have the same resistivity but their individual resistances will depend on their shapes. In this labatorial, you will explore this connection between geometry and resis- tance by using objects made of Play-Doh TM as resis- tors in a circuit. Learning Goals: To understand how the resistance of an object depends on its geometric properties. Preparation: Halliday, Resnick, and Walker, “Fundamentals of Physics” 10th edition, Wiley: 26.1–26.5 Equipment: Anatek power supply, digital multimeter, 3 banana plug connecting cables, 2 alligator clips, 2 aluminum plates, 2 voltage probes, Play-Doh TM , ruler, computer with LoggerPro software. Note that there is an equation sheet at the end of this worksheet. 1
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Phys 259, Labatorial 7, Winter 2017 1 Resistance is a Geometrical Property Every material has an intrinsic property known as the resistivity ρ . Objects made out of a material have a property called the resistance R that depends on the object’s geometry. The relationship between resistance and resistivity is R = ρL A (1) where L is the length of the object and A is its cross-sectional area perpendicular to its length. Consider a solid metal cylinder of length L and radius r . You measure the resistance of this cylinder and find it to have a value R . Question 1 : If you cut the cylinder in half so that you had two pieces each of length L/ 2, as shown in the diagram, what would be the resistance of each piece according to Eq. (1)? in series? Explain. Question 4 : If you took the two pieces arranged side-by-side as shown and considered them a single object of length L/
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  • Summer '19
  • Orders of magnitude, Electrical resistance

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