On a breadboards, hook up an IR LED to provide an infrared light source for signaling the phototransistor as shown in Figure 2 below. Use a pushbutton switch to turn the IR LED on and off. Note that the pushbutton does not require any resistors to ground as it only needs to control when the power enters the power rails on your protoboard. The IR LED will drop approximately 1.35 volts and should be operated with ~100 mA of current.

Q1: Calculate the value required for the resistor labeled R in the circuit below to achieve these design specifications.
Q2: Now calculate the power that you expect this resistor to absorb (remember the formulas for power in terms of current and resistance)

A3-mm-thick panel of aluminum alloy (k 177 w/m-k, c 875 j/kg-k and ? = 2770 kg/m) is finished on both sides with an epoxy coating that must be cured at or above t,-150°c for at least 5 min. the production line for the curing operation involves two steps: (1) heating in a large oven with air at ts,0-175°c and a convection coefficient of h, 40 w/m2. k, and (2) cooling in a large chamber with air at 25°c and a con- vection coefficient of he 10 w/m2.k. the heating portion of the process is conducted over a time interval te which exceeds the ime required to reach 150°c by 5 min (h = r + 300 s). the coating has an emissivity of ? = 0.8, and the temperatures of the oven and chamber walls are 175 and 25°c, respectively. if the panel is placed in the oven at an initial temperature of 25°c and removed from the chamber at a safe-to-touch tempera ture of 37°c, what is the total elapsed time for the two-step curing operation?