Sciencemadness Discussion Board
Not logged in [Login ]
Go To Bottom

Printable Version  
Author: Subject: Calculating electrical resistance of an aqueous solution?
Upsilon
National Hazard
****




Posts: 392
Registered: 6-10-2013
Member Is Offline

Mood: No Mood

[*] posted on 3-11-2015 at 14:02
Calculating electrical resistance of an aqueous solution?


I'm tired of using these wimpy half-amp power adapters for my electrolysis experiments, so I'm going to start using a 12V deep-cycle battery instead. I don't know how many amps it can put out, but I imagine it is at least 30 or so. Regardless I don't want it putting out its max amps for the experiment to preserve its lifetime. So, the question becomes, how can I calculate the electrical resistance of an aqueous solution where all parameters are known (the substance, its concentration, distance between electrodes, etc)? I want to know how to adjust these parameters in order to achieve a current of a few amps.

[Edited on 4-11-2015 by Upsilon]
View user's profile View All Posts By User
battoussai114
Hazard to Others
***




Posts: 235
Registered: 18-2-2015
Member Is Offline

Mood: Not bad.... Not bad.

[*] posted on 3-11-2015 at 14:26


Use a multimeter to check for the resistance, probably easier than calculating.



Batoussai.
View user's profile View All Posts By User
Upsilon
National Hazard
****




Posts: 392
Registered: 6-10-2013
Member Is Offline

Mood: No Mood

[*] posted on 3-11-2015 at 14:42


Quote: Originally posted by battoussai114  
Use a multimeter to check for the resistance, probably easier than calculating.


Probably, but I'm still interested in knowing how to do something like this. Also, there are other benefits to calculating it, like knowing the exact concentration, electrode distance, etc. necessary as opposed to constantly tweaking them in a trial and error fashion.

[Edited on 3-11-2015 by Upsilon]
View user's profile View All Posts By User
Aurium
Harmless
*




Posts: 46
Registered: 4-10-2015
Member Is Offline

Mood: Energetic

[*] posted on 3-11-2015 at 14:59


An interesting question. (ultimately useless but still) :P

Well my idea on the processes involved is one of transport of the charged chemical species (ions) bumping into non charged species and losing momentum, reaching an equilibrium drift velocity.
How to calculate this drift velocity? In liquids I have no clue. I guess something to do with stochastic physics.

If you want to get to the answer, as in an actual value instead of an approximation based on some 1D model, you'll find necessary to use a simulation software, like comsol.
It's the best way to input all your electrode geometries etc etc, and let the program model it until it spits out a number for your resistance.

That 1D simplified model would be curious nonetheless.
View user's profile View All Posts By User
phlogiston
International Hazard
*****




Posts: 1353
Registered: 26-4-2008
Location: Neon Thorium Erbium Lanthanum Neodymium Sulphur
Member Is Offline

Mood: pyrophoric

[*] posted on 3-11-2015 at 15:26


It is great if you are simply interested in the theory behind it, but realistically trying to predict it with any accuracy for messy, practical cells used for synthesis in an amateur setting is going to be nearly impossible.

To regulate the current, changing the inter electrode distance is a good method. Lowering the distance between the electrodes reduces ohmic losses.

Look up molar conductivity to read more on the theory behind electrolyte conductivity.

[Edited on 3-11-2015 by phlogiston]




-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer
View user's profile View All Posts By User
blogfast25
Thought-provoking Teacher
*****




Posts: 10340
Registered: 3-2-2008
Location: Old Blighty
Member Is Offline

Mood: No Mood

[*] posted on 3-11-2015 at 16:06


Quote: Originally posted by battoussai114  
Use a multimeter to check for the resistance, probably easier than calculating.


It's really not that easy. Accurate measurements are made with AC, not DC, see e.g.:

http://web.mit.edu/dsadoway/www/83.pdf




View user's profile Visit user's homepage View All Posts By User

  Go To Top