Labs 1 and 2: Mystery Boxes and Devices

Lab 1L.6 asks readers to measure the VITC of two mystery devices concealed in plastic 35mm film cans and Lab 2L.1.1 requires you to determine the values of a mystery resistor and capacitor.  (If someone else has set these up for you stop reading now !  You don’t want to spoil the fun of figuring out what they are on your own. In fact, if no one has, stop reading now and go get someone to make these up for you so you can enjoy the hunt.)

Note that Figure 1L.10 in the book showing the experimental setup to test the Mystery Devices is incorrect. See the Errata page for the correct figure.

Lab 1 Mystery Devices

The two-terminal mystery devices of Lab 1 are hidden in plastic 35mm film containers. (These are still available on Amazon and eBay, although only eBay seems to have the older type with the flat lid; the ones on Amazon are the newer type with an indented lid.)

Lab 1 Mystery Devices A and B

Mystery Device A is pretty simple.  It is a 33 Ohm, 2W resistor.  Higher wattage 33 Ohm resistors will work as well. (If you don’t have one handy, you could use eight 270Ω, 1/4W resistors in parallel.)

Mystery Device B is a #47 lamp.  This (and all filament light bulbs) is an odd device in that it has a negative resistance curve — as you increase the voltage the filament heats up and the resistance increases. See §8.N.4.2.  (The #47 lamp is designed for 6.3V, which is why the text cautions you not to exceed 7 volts when testing the Mystery Devices.)

Lab 2 Mystery R and C

The mystery resistor and capacitor are easy to make — just cover up the devices with electrical (or other opaque) tape.  The capacitor is a 100nF and the resistor is a 1kΩ.