lec5 - ENGR 111 Lecture 5 Reading: Chapters 19, 20 Class...

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ENGR 111 Lecture 5 Reading: Chapters 19, 20 Class notes
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Fall 2004 Review of Last Class z Ohm’s Law V = I * R z KCL/KVL and Ohm’s law allow us to compute equivalent resistances z Resistances in series R = R1 + R2 z Resistances in parallel 1/R = 1/R1 + 1/R2 z Resistances in series => Voltage Dividers z Resistances in parallel => Current dividers
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Fall 2004 Power z Power = rate at which energy consumed or produced z Power, symbol (P), Units (Watts) z P = I * V z Water analogy, amount of water (current), the height of the drop (voltage) determine power z Horsepower ratings on engines, wattage ratings on bulbs
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Fall 2004 Energy z Charge moving through battery converts chemical energy to electrical energy z Energy U = Q V = (charge * Voltage) z Energy units (Joules, KWh), symbol (U) z Remember Power = rate of energy consumed = dU/dt = d/dt (QV) = dQ/dt V = I V z Utility bill in KWh = 1000 Watts over an hour = 1000 Watts * 3600 sec = 3.6 MJoules
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Fall 2004 Energy z Energy use of increasing importance z So many electrical gadgets, computers, networks, phones, cell phones, … z Portable devices laptops, cell phones should run for long periods after charging z Environmental concerns, power scarcity
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lec5 - ENGR 111 Lecture 5 Reading: Chapters 19, 20 Class...

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