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Transcript
ELET 1300 Closed Book & Notes EXAM 31 Fall 2001 Text equation sheet is allowed NAME: SHOW YOUR WORK!! Problem # 1 Select the best answer for the following questions: A. The current carriers in a metal conductor are: a. b. c. d. protons ions atoms electrons B. The force which drives current through a load is: a. b. c. d. voltage watts amperes coulombs C. As temperature rises, metal resistance : a. b. c. d. decreases stays the same increases becomes negative D. The circular mil is a measure of : a. b. c. d. resistance area length resistivity E. A superconductor is a material with : a. zero resistance b. copper c. very high resistance d. low voltage F. The kilowatthour (kwh) is a measure of : a. b. c. d. power voltage current energy Problem # 2 How many feet of wire do I need to get 50 from aluminum wire with a radius of 0.5 mm? The resistivity of aluminum is 2.83 x 10-6 -cm Problem # 3 Given the following circuit with a 1.2 volt battery and 5 k resistor: 5 k 1.2 V + ELET 1300 EXAM #1 Fall 2001 (a) What is the magnitude (in A) and direction (up or down) of the current through the resistor? (b) How much power in mW is dissipated by the resistor? (c) If the battery has a lifetime rating of 1.25 Ah, how many days will the battery be able to supply this current? Problem 4: A 0.25 horsepower electric motor has an efficiency of 78%. It operates from a source of 120 V. (1 hp 746 watts) (a) What is the power input to the motor in watts? (b) What is the current though the motor? (c) How many kilowatthours (kwh) are consumed by the motor if it operates for 10 hours?