p240_ct10_w12_feb_7 - Physics 240 Winter 2012 Lecture #10...

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Physics 240 Winter 2012 Lecture #10 Dr. Dave Winn 2405 Randall [email protected] My Office Hours (1416 Randall Lab) Monday 1pm-3pm Tuesday 1pm-3pm Thursday 2pm-4pm (Prof. Gidley) Learning Assistant Office Hours Tuesday 4-8pm Thursday 4-6pm Also in chat room Tue/Thu evening!
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Two copper wires of different diameter are joined end-to-end, and a current flows in the wire combination. When electrons move from the larger-diameter wire into the smaller-diameter wire, Q25.1 A. their drift speed increases. B. their drift speed decreases. C. their drift speed stays the same. D. not enough information given to decide
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Electrons in an electric circuit pass through a resistor. The wire has the same diameter on each side of the resistor. Compared to the potential energy of an electron before entering the resistor, the potential energy of an electron after leaving the resistor is A. greater. B. less. C. the same. D. not enough information given to decide Q25.3
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Moving beyond electrostatics… • How to make charge move? – Start with a conductor (through which charge can flow) – Apply an electric field • If the conductor is isolated , charge moves to cancel the field • After this charge stops moving ------------------- +++++++++++
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Moving beyond electrostatics… How to make charge move? – Start with a conductor (through which charge can flow) – Apply an electric field If the conductor is connected in a circuit , charge moves but never manages to cancel the field; it continues in a steady flow, a “current” - -
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The water analogy… • A conductor is like a tank of water • Tilting it is like applying an electric field • If it is tilted, and connected to a source of water and a sink, a fluid current will flow
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Moving beyond electrostatics… • Electric field through this region requires a change in potential across the conductor V = Ed • To keep a current flowing, I have to maintain this potential difference across the conductor d V high V low
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• Maintaining the potential difference across the conductor is like keeping the surface of the water tilted. • Requires putting water in at the top and
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This note was uploaded on 02/15/2012 for the course PHYS 240 taught by Professor Winn during the Winter '11 term at University of Michigan.

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p240_ct10_w12_feb_7 - Physics 240 Winter 2012 Lecture #10...

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