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HW1a - a What is the total stored energy in joules b...

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18-220 Fall 2008 ________________________________________________________________________ HW SET #1 (DUE AT THE BEGINNING OF CLASS, SEPT 8) ________________________________________________________________________ Reading : Chapter 1 in Semiconductor Devices and Technology Note: All submitted homework must include your full name, first name first, last name last; lab section; and recitation section if different from your lab section, printed in the upper right-hand corner. Problems: Power, energy, and unit conversions 1. A commuter drives an electric car with initially uncharged batteries from the top of the Berkeley Hills (500 m above sea level) to a coffee shop on Solano Avenue (200 m), recovering 80% of the gravitational potential energy as electrical stored energy in the batteries. The car weighs 2450 kg including driver.
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Unformatted text preview: a) What is the total stored energy in joules? b) Suppose all of this stored energy is used to power a 60 W light bulb. How long can the light bulb be operated? 2. An engineer is designing a 2 kW heater element for a furnace. The heater element needs to operate from a 220 V source and is to be made from 18 gauge nichrome wire (0.040 inches in diameter). The conductivity of nichrome is 0.9 × 10 4 1/ Ω⋅ cm. a) Determine the current flowing through the heating element. b) Determine the length of the nichrome wire required. c) Would it be practical to use copper wire for this heating element? Give one or two reasons to justify your answer. From Chapter 1 in Semiconductor Devices and Technology Problems 2, 3, and 6. (physical constants are on page 43)...
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