# ch31 - Chapter 31. Current and Resistance Lights, sound...

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1 Chapter 31. Current and Resistance Lights, sound systems, microwave ovens, and computers are all connected by wires to a battery or an electrical outlet. How and why does electric current flow through a wire? Chapter Goal: To learn how and why charge moves through a conductor as what we call a current.

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2 Topics: The Electron Current Creating a Current Current and Current Density Conductivity and Resistivity Resistance and Ohm’s Law Chapter 31. Chapter 31. Current and Resistance Current and Resistance
3 Topics: The Electron Current Creating a Current Current and Current Density Conductivity and Resistivity Resistance and Ohm’s Law Chapter 31. Chapter 31. Current and Resistance Current and Resistance You are responsible for all of Chap 31

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5 What quantity is represented by the symbol J ? A. Resistivity B. Conductivity C. Current density D. Complex impedance E. Johnston’s constant

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6 A. Resistivity B. Conductivity C. Current density D. Complex impedance E. Johnston’s constant What quantity is represented by the symbol J ?
7 The electron drift speed in a typical current-carrying wire is A. extremely slow ( ! 10 –4 m/s). B. moderate ( ! 1 m/s). C. very fast ( ! 10 4 m/s). D. Could be any of A, B, or C. E. No numerical values were provided.

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8 A. extremely slow ( ! 10 –4 m/s). B. moderate ( ! 1 m/s). C. very fast ( ! 10 4 m/s). D. Could be any of A, B, or C. E. No numerical values were provided. The electron drift speed in a typical current-carrying wire is
9 All other things being equal, current will be larger in a wire that has a larger value of A. conductivity. B. resistivity. C. the coefficient of current. D. net charge. E. potential.

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10 All other things being equal, current will be larger in a wire that has a larger value of A. conductivity. B. resistivity. C. the coefficient of current. D. net charge. E. potential.
11 The equation I = ! V/R is called A. Ampère’s law. B. Ohm’s law. C. Faraday’s law. D. Weber’s law.

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