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physics cheat sheet exam3

physics cheat sheet exam3 - 17 An aluminum wire a= 50^2 mm...

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17. An aluminum wire a= 50^2 mm placed along the x -axis passes 10^3 C in 1 h. One free electron for each aluminum atom. Current? current density? drift speed? mass density is 2.7 34. An electrician tests for a short circuit by putting a potential difference of 1.5 V across two neighboring parallel wires that would be independent of each other if there were no short. A current of 0.14 A then flows in the wires. The wires consist of material with a resistivity of 1.7*10^-8, diameter of 0.24 mm. The short makes the wireslike a single wire, how far away? 76. Buildings have circuit breakers, devices that switch the current off when it exceeds a critical value, to protect the electrical system from damage. One circuit for a building’s lights has a 15-A breaker. (a)What is the maximum power that can be delivered by a 110-V line to this circuit? (b) How many lightbulbs, each requiring 75 W, can this circuit handle? 82. One month’s electricity bill is $25.33; the cost of electricity is 8 cents kWh. All appliances at 120 V. How many electrons that month?
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