edit: I was very sleep deprived and my mind blanked out on the answer. Just find the voltage of the known resistor w/ the ohmemeter, and use ohm's law (i=v/r) to get the current, then use the current with the unknown r's voltage & ohm's law to get the resistance. Sorry to waste everyone's time.
I have an unknown resistor and a 1k resistor. I can only use a voltmeter, and I can place them in series. How would I go about finding the value of unknown resistor?
I have no idea where to even start with this- I have the voltage source (9v) but don't know what to do to find the rest. I suspect I have to get the current (as it is the same through all components) but I don't have the total resistance ( i=v/r) to get the current. If I calculate current with just the 1k resistor then it wouldn't be accurate.
Best Answer
Put the two resistors in series, then connect the voltage source across both of them. The voltage will drop across each in proportion to their resistance, because, being in series, they share the same current, and the voltage will be current times resistance.
So if resistance values are $R_1$ and $R_2$, and the voltages are $V_1$ and $V_2$, then you know that
$$\frac{V_1}{V_2}=\frac{R_1}{R_2}$$