Let’s assume that you have several resistors (from your component kit) of unknown
resistance and (very surprisingly) no ohmmeter to test them. Let’s further assume that you
have Arduino UNO, a computer with installed Arduino IDE, and one resistor of known
resistance (say, 1 kΩ).
Your assignment is to propose a method allowing you to measure the resistance utilizing
the items you have (Arduino, wires, computer, and one “reference” resistor of known
resistance). Implement your method: make the necessary connections and create the
appropriate Arduino code (you may use Processing, C/C++, or Assembly if prefer). Use the
Serial Monitor to communicate the measured resistance to a computer. Test the
functionality of your “home-brew ohmmeter” on several resistors with the resistance both
below and above the reference (that you assumed as 1 kΩ, for instance).
This looks like a homework assignment or school project. What do you have so far?
And your question is?
Do you know what a voltage divider is?
.
That looks like a homework assignment to me. We're really not here to do your homework for you. You should review your notes on resistors - presumably you've already learned about resistors in a "voltage divider" configuration, and how to treat resistors in series, which is what the real key here is.
If you have specific questions, go ahead and ask - but don't expect us to do everything for you when you copy/paste an assignment into the forum.