2049_ch27A - Circuits PHY2049: Chapter 27 1 What You...

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PHY2049: Chapter 27 1 Circuits
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PHY2049: Chapter 27 2 What You Already Know Î Nature of current Î Current density Î Drift speed and current Î Ohm’s law Î Conductivity and resistivity Î Calculating resistance from resistivity Î Power in electric circuits
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PHY2049: Chapter 27 3 Chapter 27: Electric Circuits Î Work, energy and EMF Î Single loop circuits Î Multiloop circuits Î Ammeters and voltmeters Î RC circuits and time constant
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PHY2049: Chapter 27 4 Reading Quiz for Chapter 27 Î The electric current is defined as: ± (1) amount of charge per time ± (2) amount of charge per area ± (3) amount of charge per volume Î When resistors are connected in series ± (1) the current in each resistor is different ± (2) the current in each resistor is the same ± (3) the voltage in each resistor is the same Î Which of the following is not related to Kirchhoff’s Rules? ± (1) conservation of charge ± (2) conservation of energy ± (3) conservation of momentum
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PHY2049: Chapter 27 5 EMF Î EMF device performs work on charge carriers ± Converts energy to electrical energy ± Moves carriers from low potential to high potential ± Maintains potential across terminals Î Various types of EMF devices ± Battery Electrolytic reaction ± Generator Magnetic field ± Fuel cell Oxidation of fuel ± Solar cell Electromagnetic energy ± Thermopile Nuclear decay Î Example: battery ± Two electrodes (different metals) ± Immersed in electrolyte (dilute acid) ± One electrode develops + charge, the other – charge
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PHY2049: Chapter 27 6 Common dry cell battery
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PHY2049: Chapter 27 7 Electrons in the wire Î If the electrons move so slowly through the wire, why does the light go on right away when we flip a switch? ± Household wires have almost no resistance ± The electric field inside the wire travels much faster ± Light switches do not involve currents ± None of the above
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PHY2049: Chapter 27 8 Electrons in the wire, part 2 Î Okay, so the electric field in a wire travels quickly. But, didn’t we just learn that E = 0 inside a conductor?
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2049_ch27A - Circuits PHY2049: Chapter 27 1 What You...

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