1. A volt-ohm-milliampmeter (VOM) with a sensitivity of at least 50,000 ohms per volt or a digital voltmeter (DVM). If you have to purchase one then get a DVM. Radio Shack carries a line of DVM's that are relatively inexpensive and more than adequate for the experiments in this book.
2. A variable voltage source of up to 6 volts. You can make a simple but effective voltage source from four 1.5 volt batteries. See figure below.
3. Hook up wire. Preferably test leads with alligator clips on the end. You can also purchase these at stores like Radio Shack.
4. A basic scientific calculator. However if you are reading this you obviously have a Macintosh. There is a very powerful math program that will allow you to calculate solutions to problems and plot data that you will take in the experimental part of this lesson. The program is MathPad 2.3.5. It is available on AOL as well as at the following web page:
http://pubpages.unh.edu/~whd/MathPad
or ftp at: unhggs1.unh.edu /pub/mac/MathPad-235.bin
As of this writing it is freeware. If you decide to use it let Mark Widholm the author and programmer know how much you appreciate it.
 
By moving the tap point on the battery array you can apply 1.5 Volts, 3.0 Volts, 4.5 Volts and 6 Volts to the 1000 ohm resistor. I have shown the batteries connected in series with jumper wires. However the simplest and easiest way is to do this is to get a battery clip from a source like Radio Shack. You can use alligator test leads to jumper between the tabs on the battery clip. This also makes it easier to replace batteries. You can also add more batteries in the series to obtain higher voltages.
