p240+feb+8+problems

# p240+feb+8+problems - What is the current in the silver...

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25.12 A copper wire has a square cross section 2.3 mm on a side. The wire is 4.0 m long and carries a current of 3.6 A . The density of free electrons is 8.5∙10 28 electrons/m 3 . Find the magnitudes of (a) the current density of the wire and (b) the electric field in the wire. (c) How much time is required for an electron to travel the length of the wire?

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25.58 A 2.0- m length wire is made by welding the end of a 120- cm -long silver wire to the end of an 80- cm long copper wire. Each piece of wire is 0.60 mm in diameter. The wire is at room temperature, so the resistivities are 1.47∙10 -8 Ω∙m for silver and 1.72∙10 -8 Ω∙m for copper. A potential difference of 5.0 V is maintained between the ends of the 2.0- m composite wire. (a) What is the current in the copper section? (b)
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Unformatted text preview: What is the current in the silver section? (c) What is the magnitude of E in the copper? (d) What is the magnitude of E in the silver? (e) What is the potential difference between the ends of the silver section of wire? • 25.66 The region between two concentric conducting spheres with radii a and b is filled with a conducting material with resistivity ρ . (a) Show that the resistance of the spheres is given by: • (b) Derive the expression for the current density as a function of the radius, in terms of the potential difference V ab between the spheres. (c) Show that the result in part (a) reduces to: • when the separation between the spheres L=b-a is small....
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p240+feb+8+problems - What is the current in the silver...

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