This video shows a potato used as a potentiometer - fun but don't try it at home! (If you ask nicely we might try it using a safe p.d. like 24 V and a high resistance voltmeter) http://youtu.be/1l2kgi4DOOk
The website below might be useful, particularly for the potential divider calculator. Also students aiming at high grades could make sure that they understand the approximations section - understand, not learn!!. (Please note, if only one connection is shown for Vout, the other one is the negative of the supply, usually labelled 0 volts in electronics circuits.) https://learn.sparkfun.com/tutorials/voltage-dividers/ideal-voltage-divider
Further work, more examples to practice on. http://www.youtube.com/watch?v=rIEnMpgIaU
However this video makes the calculations look more complicated than they need to be as he leaves the current value as a calculation of V/R instead of working out the actual value. For example in this screenshot 5V/(2+3)kilo_ohms is of course equal to 0.0010 A (1.0 mA) . This approach can be useful as it shows directly how the ratio of the resistors is the key factor in working out the output p.d. See further note and screenshot below the embedded video (at the bottom of this blog)
Note: Instead of labelling V1, V2 as the voltages across the resistors he labels them V2kohm instead, as you can see in this screenshot. The final answer for V2kohm is clearly 5V x (2/5) = 2 Volts!
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