How to Calculate Current Density (Petri Dish/Graphite 0.7 mm)

AI Thread Summary
To calculate current density in the described setup, the area must be determined based on the distance between probes and the geometry of the petri dish. The formula for current density is J = I / A, where I is the measured current and A is the cross-sectional area through which the current flows. When measuring at 1 cm intervals in an 8.7 cm diameter dish, the area can be approximated using the effective width of the path between probes. The discussion also raises the question of whether to treat the current path as a linear region in 2D or as a gradient in 3D, which impacts the calculation of current density. Understanding these factors is crucial for accurate measurements in electrochemical experiments.
TGH904
Hello all,

I have a petri dish 8.7 cm in diameter filled with 20 mL of TSB media. I have set up a .7mm graphite at the 0cm mark of the diamter and measured current at 4.6Volts over the entire distance of the petri dish (8.7cm) with .5 cm step sizes. For example:

When the probes are 1cm apart I am reading a current of 2.8mA.

I was wondering how I can calculate a current density for all the known information.

Current Density (J) = Current (I) / Area (A)

How could I calculate the area if I am 1 cm apart in a 8.7 cm petri dish?
 
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Hello. You can estimate resistivity by filling a long and thin tube with that liquid and calculate its resistance. It adds some more info relating to the voltage too.
 
What I want to understand about current density when measuring do I treat the path of current in a liquid as a linear region in 2D, or as a gradient in 3D
 

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