Elec. Current and DC circuits

# Elec. Current and DC circuits - PHY 2049C General Physics B...

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PHY 2049C – General Physics B Fields, Circuits, Waves, Light Today: 1) Currents 2) Ohm's Law 3) Power

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Electric Current So far, we have studied static electricity ; What forces act on charges etc, what energy Now let's move things around: When a potential difference is applied, the charges in the conductor begin to move . and continue to move . We call that electric current. current current Battery +V -V
Electric Current With the switch open, the battery will push a few electrons into the wire at the -pole , and pull out a few at the +pole the process stops, because the charges repel each other. (~like charging a capacitor)

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Electric Current With the switch closed, the battery takes out electrons at the +pole and continuously puts new ones in at the -pole . Analogy: Water in a pipe : Battery=pump Voltage=pressure bulb = Tight spot “Tight spot” =lightbulb c u r e n t
Question You have just put fresh batteries in your flashlight and it is working nicely. Now suppose that you remove both of the batteries and reinsert them backward. Despite the fact that the both batteries are reversed, they connect properly to one another and to the flashlight, so that there are no connection problems in the flashlight. As the result of this battery reversal, the flashlight will A) work in reverse, lighting up when you put its switch in the "off" position and not lighting up when you put its switch in the "on" position. B) remain lit regardless of the position of its on-off switch.

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## This note was uploaded on 06/29/2010 for the course PHY2049C PHY2049C taught by Professor Duke during the Summer '10 term at FSU.

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Elec. Current and DC circuits - PHY 2049C General Physics B...

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