Act13_sol - Period 13 Activity Solutions: Electrical...

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49 Period 13 Activity Solutions: Electrical Resistance and Joule Heating Activity 13.1: What Does the Electrical Resistance of a Wire Depend Upon? a) Resistor length, L Use a multimeter to measure the resistance of the wires on the green board. 1) Measure the resistance of the thin 30 cm nichrome wire. _________ 2) Measure the resistance of the 15 cm nichrome wire. ______________ 3) Does resistance R increase or decrease with increasing length L ? The resistance increases with increased length. b) Resistor thickness, A 1) Using a multimeter, measure the resistance of the thick 30 cm wire. _____________ 2) Does resistance R increase or decrease with increasing cross-sectional area A ? The resistance decreases with increased cross-sectional area (thickness) of the wire . c) Resistivity: The resistance of wires also depends upon the resistivity ( ρ ) of the wire material. Use connecting wires to connect a 3-battery tray, a one-bulb tray, and a piece of copper in series. Note the brightness of the bulb. Then replace the copper with other materials and note the brightness of the bulb. Indicate which materials have high resistance, intermediate resistance, and low resistance. Material Bulb brightness Resistance a) Copper brightest low b) Plastic not lit high c) Graphite barely lit intermediate d) Glass not lit high e) Iron bright low d) Relationship between R, L, A , and r We have found that the resistance of a wire R is directly proportional to length L and inversely proportional to the cross-sectional area A. For a given type material, the resistivity
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Act13_sol - Period 13 Activity Solutions: Electrical...

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