PHYS 102 1nd Edition Lecture 11 Outline of Last Lecture I. Resistance, Resistivity, and Ohm’s Law Outline of Current Lecture II. Electrical Energy and PowerCurrent LectureII. Electrical Energy and Power A. Electrical Energy and Power Equations P = Energy/ Time = I V= J / t = Watt (W) P = Energy/ Time ~PE V = PE/ q PE = q V P = Energy/ time = qV/ t P= IV B. Electrical Energy and Power Applications 1. pg. 612 #34 If electrical energy costs $0.12 per kilowatt-hour, how much does it cost (a) burn a 100-W lightbulb for 24 h? (b) Operate an electric oven for 5.0 h if it carries a current of 20.0 A at 220 V? (b) P = IV = (20)(220) = 4400 Watts These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.t = 5 hours Energy = pt = 4400 W (5 hours) = 22000 WhEnergy = 22,000 Wh = 22 kWh Cost = $0.12 X 22 kWh = $2.64 2. Common Voltages in Everyday Appliances a. Voltage in our homes/offices: 110-120 V b. Overseas: 220-240 Vc. In US & overseas: the current is AC (alternating/oscillating), not DC. i. In the US, it is oscillating 55 times per second, or 55 Hz. ii. Overseas, it is 60
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