When performing this test does one absolutly have to use the conductance sensor? One could not just connect one cable from the multimeter to the 9 volt battery to the liquid and then have the other wire go directly to the liquid? I am afraid that not having it will mess up the formula I'm suppose to use at the end...Is that true? Please help soon i want to finish this project by the end of the week! Thanks so much!
P.S.
At the end of the experiment you are suppose to use the formula of cunductance= current divided by voltage. I understand the formula, but before that you are suppose to divide your answer by 1,000,000 from microamps to amps or divide by 1,000 from milliamps to amps. But when you type that into the calculator it doesn't work or comes up with a compilcated answer. Do you know what to do about this?
For example if orange juice is 0.7 microamps and then you divide that by 1,000,000 the calculator gives an answer of:
7E -7. What does that mean? How do I solve that or can I?
Please please please help!!!!
Last edited by PeaceLoveSmile on Tue Dec 29, 2009 5:36 pm, edited 1 time in total.
PeaceLoveSmile - As I understand what you are doing, you are measuring the conductance (the reciprocal of resistance, that is, G=1/R) of the different fluids, orange juice and sports drinks using a milliameter and a 9 volt battery. Both types of liquids will conduct current - orange juice because of the ionic nature of the citric acid in water, and commercial sports drinks because of their inherent 'electrolyte' qualities based on their contents of mineral salts, carbohydrates and other chemical compounds. I don't know what the hypothesis of your project is, so I'm not sure how this will correlate into your experiment.
The issue of translating units is somewhat simpler. The basic equation for resistance is R=E/I, where the unit of resistance, R, is an Ohm, E is a Volt and I is an Ampere. For conductance, the formula is inverse, G=I/E, where G, the unit of conductance, is the Mho (Ohm backwards), or now known as the Siemen, R is the resistance in Ohms. To translate your readings from microamps to amperes, divide by 1,000,000. To translate milliamps to amperes, divide by 1,000. Your calculator is using 'scientific notation' and is expressing 0.7 microamperes divided by 1,000,000 to be 7x10 to the -7th power, or .0000007 amperes. If you haven't studied scientific notation, just use the old math with all the zeros and decimal point. Hope this helps.
Rick,
Thank you very much for your help... My hypothesis for this experiment is that orange juice will have a higher conductance and therefore higher level of electrolytes. I now have come across another question... but I'm not sure if you'll be able to answer.
With this project you have to use a mulimeter. Today I was performing the experiment and i was moving from on test subject to another and all the sudden it stopped working. I changed the battery and wires. I reconnected everything and it still wouldn't read. It had worked for about 15 trials. My dad, an electrician, has looked it over and over. He said the wring is right and the meter is working. Do you know what the problem is? Thanks again.
PLS - First, lets test the multimeter. Use your 9 volt battery to do a DC voltage test. That will also test whether your battery is still good. If you get a low voltage reading the battery may be spent, and although it will show a few volts there will be little current provided. Next, try a current range. Use your 9 volt battery and find something like a 1,000 ohm resistor to put into the circuit using an appropriate range setting. That combination will show something close to 9 milliamperes of current flow. If those functions don't work you may have a blown protective fuse inside your meter. A multimeter usually has AC/DC voltage and DC current ranges and also an Ohmmeter to measure resistances. In most simple multimeters the battery is used only in the Ohmmeter function. With your setup of using a 9 volt battery as a current source make sure you are using the DC milliammeter/microammeter ranges only for your measurements. If for some reason you were using the ohmmeter function you could damage the meter (your 9 volt battery in series with the internal battery and multiplier resistors) or you could be in the circuit with reverse polarity and could drive the meter into some other state. I don't know if you are using a digital or analog instrument. Clean your electrodes. By passing current through them in the electrolyte you could be causing an oxide to form on your leads, limiting or preventing current flow. Lot's of variables, you may learn a lot more if you can correctly diagnose and repair your setup.
As long as your teacher is OK with it, I think you can definitely do this experiment. It's quite common for the same type of experiment to be done by different students--especially when you consider the huge number of students doing science fair projects in the United States and around the world. If you decide to do a similar project and have questions you would like the Experts to answer, please start a new topic. Doing so will help ensure your questions are answered in a timely fashion.
