Testing Conductivity of Food
Date: Winter 2011-2012
How would you test the conductivity of a pickle and a cucumber?
An approximate formula for resistance is the cross-sectional area of the pickle divided by the product of conductivity and length. Measure the diameter across the pickle. Use this to calculate the area across the pickle. Measure the length of the pickle. Insert wires just a little into each end of the pickle to measure its resistance. Use an ohmmeter, or a multimeter set to measure resistance, to measure the end-to-end resistance. Using a voltmeter and an ammeter can work, but the current could be too high for the ammeter. This gives you enough information to find conductivity.
If you do not have an ohmmeter, but do have two voltmeters and an adjustable resistor, here is another way. Connect the pickle in series with the adjustable resistor set to what you consider greater than the pickle's resistance. A battery will work as a power source for the circuit. Connect one voltmeter across the resistor and one across the pickle. Adjust the resistor until the resistor and pickle have the same voltage. At this point, the resistor has the same resistance as the pickle.
Dr. Ken Mellendorf
Illinois Central College
Both a pickle and a cucumber have rather large conductivity since both
contain a lot of water.
The pickle especially will have a high conductivity because of the salt
content and the vinegar.
It is not that easy to measure samples that have high conductivity.
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Update: June 2012