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    Resistance Based Physics Problems

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    1. You've made the finals of the Science Olympics! As one of your tasks, you're given 2.0g of copper and asked to make a cylindrical wire, using all the metal, with a resistance of 2.0omega .

    a) What length (l) will you choose for your wire?
    Express your answer in meters to two significant figures.

    b) What diameter (d) will you choose for your wire?
    Express your answers in millimeters to two significant figures.

    2. The relatively high resistivity of dry skin, about 1×10^6 omega⋅m, can safely limit the flow of current into deeper tissues of the body. Suppose an electrical worker places his palm on an instrument whose metal case is accidently connected to a high voltage. The skin of the palm is about 1.5 mm thick.

    a) Assume the area of skin on the worker's palm that would contact a flat panel is 1.3×10^−2 m^2 , then calculate the approximate resistance of the skin of the palm.
    Express your answer to two significant figures and include the appropriate units.

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    Solution Preview

    1. mass of copper, m = 2.0 g = 2.0*10^(-3) kg
    resistance, R = 2.0 ohm

    density of copper, D = 8.96*10^3 kg/m^3

    Hence, volume, V = m/D = 2.0*10^(-3)/(8.96*10^3) m^3

    Resistivity of copper, rho = 16.78*10^(-9) ohm.m

    Let us assume, length = L and cross-sectional area = ...

    Solution Summary

    Two problems of relation among resistance, resistivity, length and cross-sectional area are solved. All calculations are included.