HW1.E40.Aut11 - chargers(which we assume requires 2 hours...

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E40 Autumn 2011 Homework 1 Due 5:00 pm, Wednesday, October 5, 2011 Please write your Name and Lab Section Time on the front page. 1. The current i (t) in a wire is given by: i (t) = (1.5A)sin[(2 π )(1000) t ], where t is in seconds. a) Plot the current from t = 0 to t = 500 μ s. (1 μ s = 10 -6 s) b) Find the charge in Coulombs that passes through the wire over the interval t = 0 to t = 500 μ s. c) Find the charge in Coulombs that passes through the wire over the interval t = 0 to t = 1 ms. 2. A typical 12 V lead-acid automobile battery stores 500 W-hours of energy. There are approximately 250 million cars in the U.S. We assume that each has a single 12 V lead- acid battery – ignoring electric and hybrid cars. a) How much energy (in Joules) is stored in all the 12 V car batteries in the U.S.? b) If all of these car batteries were dead ( i.e ., discharged completely and so storing no energy) and the car owners charge them simultaneously using 12 V battery
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Unformatted text preview: chargers (which we assume requires 2 hours), what is the total battery-charging current in the U.S. in Amps? c) How much power in Watts is used during the battery charging? 3. U&M Problem 1.17. Also, find the sum of the power in all the elements, using the passive sign convention. 4. A commonly available type of resistor is rated at 1 W “power dissipation,” meaning this amount of power can be dissipated continuously in the resistor without damage. a) Determine the maximum allowable DC voltage you may apply across an 82 Ω resistor, while keeping within the 1W power limit. b) Another limitation is the resistor’s breakdown (or “flashover”) voltage, when the current will arc across the leads. For a typical 1 W resistor, flashover occurs at around 200 V. What is the maximum resistance that you can use, that is consistent with both the flashover and power dissipation limits?...
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