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Some help with Ohms and resistance? Answered

hey guys, i know there are a lot of you guys out there that deal with electrical dealings and such, and im doing a science project, dealing with electrolysis, so i decided to compare two electrolytes to see which has a lower resistance, and to see which would be more efficient therefore. SO, the only problem is, i have no multimeter, voltmeter, or anything close to it, and i don't know anybody 'round her that does..So im asking you, could you help me with seeing the resistance of-
* water (tap water)
* water with Epsom Salts
 * and water with Baking soda powder (either will work, but i would prefer powder, as baking soda is said to cause chlorine gas, and what not..whichever you have works)

If you could take a picture of yourself using the multimeter, that would be stellar, thats all for now, 
come on guys, i know you know this stuff, and i just cant figure it out, counting on you :)


Got a compass ? 

What would happen if you put a current carrying wire near it ? 

it would make a magnetic field, and disrupt the earths magnetic field for the compass, making it line up with the wire..but how does that tell resistance?

So. If you have a nice fresh battery, and a certain resistance, and say our compass  deflects 20 degrees.... With another resistance say 1/2 as much, will more or less current flow ? What will be the effect on the meter ?

This method is probably part of how Georg Simon Ohm actually DID his research.

ahh, thank you..but i think i should get some numbers to use in my presentation

i think i might use this in my presentation to prove that one is less resistive than the other, thank you! 

Like I said previously - you want to know your solutions, and arrive at figures in ohms per unit length with respect to concentration. Or be sure to make the concentrations and distance the same at least


So, i have results

3.32 m Ohms-Epsom salt
2.94 m Ohms-Baking Soda
.815 m Ohms-Plain tap water ...rather odd
1.041 k Ohms- Sulfuric Acid at about a 4% solution (500ml Water to ~20mL)

So! the actual experiment was a total failure, i left the tap water, baking soda solution and epsom salt solution electrolyze for 10 minutes, measured the difference..each one was inconclusive..less than 2mL ..i didnt get to test the Sulfuric Acid, as i had to talk to my teacher at school and she helped me with that (which by the way, adding a neutralizer like baking soda to Sulfuric acid is rather fun, try it sometime..) 

now to type up my research paper due tomorrow, and put together a posterboard and a few forms due Monday..off i go!

I've said this at least twice - know your solutions. What concentrations were they at?
De-ionised (very pure) water is in the MOhm range, your results seem to be rather high - how did you do it?
(The acid seems OK)


i was afraid they seemed high.. The pure tap water seems less resistant than those with the electrolyte (or do i not understand ohms?) ..

thank you lemonie for your help! :D 

How did you do it, how much of the minerals did you dissolve in how much water?


 500mL of water with 1tbsp of baking soda and 1tbsp of epsom salt

the sulfuric acid was about20 mL..the multimeter wires (leads?) were about 2 and a half inches apart if it matters, that i knew i had to keep constant

anywho, i do have one question for you...i had some buildup on the one lead from when i was doing the electrolysis from the baking soda. I think this would have been the negative wire..this would have been the cathode? or was it the anode..im sorry but electricity isnt my specialty and the terms confuse me.

again, thank you very, very much Lemonie! :)

No. You need to show your initiative and find a work-around.
Have you got LEDs and a battery?
Standardise some solutions:
1g/100ml, 10g/100ml, 20g/100ml etc. see what will light things, you can calculate to some extent.
Baking powder does not contain chlorine, "bleaching powder" does though.


Salty water does though. Can you crack brine to chlorine ? 

Yes I did that, years ago. Distressed the carpet a bit, smelled-a bit, I think I chlorinated Flora-spread or similar...


I read a classic science fiction story, by the late, great Colin Kapp, the Survival Game where the protagonist survives, and survives well using his technical skills - electrolysing water to make bleach as the precursor to something else.

Well you can get to chlorate, then fire & possibly explosives.


some places ive read that one of the bakin ---'s can make chlorine gas, but i always get it mixed up *sigh*, anyway i was thinking what you said about the 1g/100ml, just typed everything too fast..thats a good idea to use an LED and battery, but the calculations need to be a bit more exact..thank you

Make sure you know how your solutions are prepared, keep the electrodes at measured distances.
It's going to be relative to start, but you could get close by visual comparison. E.g. you wire one identical LED through a known resistor, change the distance between electrodes until you match the brightness. Ultimately you have to produce a figure (tied to concentration) which is Ohm per unit length. Or you go cleverer than that by differing concentrations (MS Excel graph) and get Ohms per unit length proportional to molar concentration.
It's more difficult than using a multimeter, but it's a more intensive use of your mind, and ought to score more points.


oh my...i guess i could do that. but right now i just want to get the measurements..if i find the resistance of each compound, and add them together would that work? or is resistance much more complicated than that? 

What can't you figure out ? Use some ingenuity, and make a meter.

A i dont have any electrical background, soldering iron, solder, LEDs, PCB board, breadboards, or anything such the sort

i need to figure out the resistance of plain tap water, tap with baking soda, and tap water with epsom salt (magnesium sulfate)

oh, i and i need it done by Friday (the research paper anyway) and to present it all monday/tuesday..so making right now isnt really an option 

Borrow multimeter. (Or buy one; you can get simple ones for under $10.) Set to highest resistance range. Stick probes in liquid. Measure results. Note that the results may vary depending on the size and shape of the container and placement of your test leads; if so, you should propose some theories on why that's happening, and if not you should propose some theories on why not.

The reason you do homework is to learn how to do things, not just to get the answer. One of the things you need to learn is how to allow yourself enough time to complete a project.

yea, i should probably learn to stop procrastinating...but i think ill do that some other time >.<

anywho.. i think i might be able to find one from someone at my school, im sure one of the science teachers has one, or something..maybe i could ask a guy i know that works as an electrician/janitor at the school