Week 24

Reading, etc.
Assignments & Handouts
Calculus: Strang 11.3, 12.1, 12.2 (optional, but cycloid stuff is cool!), 12.3 Read-through answers
Physics: Mazur Ch. 21 (skip section 21.8 Brayton cycle)
Electronics: Week 4: Diodes and power suppliesReading:-          Horowitz and Hill, Art of Electronics, pp. 43-53.-          Horowitz and Hayes, Lab Manual, pp. 61-74Exercises:-          Due before class Tue: HH Ch 1: 1.26, and also end-of-chapter Additional Exercises (p. 58-9) #3, #7.-          Due before class Thursday: Additional Exercises (p. 58-9) #2, #4, as well as 1.23, 1.26, 1.29. Also: Neil Problem #1:o   You want to make an LED flashlight using a 9V battery. LEDs are diodes, but they have a “forward voltage drop” that is higher – usually about 2.5V. In other words, there is a 2.5V drop across the diode in the figure below:Week 4 circuitA) To get light out of the LED, you run a current through it. For small LEDs, the maximum current they can take is about 20mA. What R value should you use to limit the current to no more than 20mA? (this is known as a “current-limiting resistor”.)B) How much power is dissipated in the resistor? How much is dissipated in the LED? What fraction of the total power dissipated is used in the LED (that’s the fraction of the power that goes to generate light)? Based on that result, does this seem like a good circuit if you want your flashlight to last a long time?