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

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SUMMARY

The discussion focuses on calculating current density in a petri dish setup using a 0.7 mm graphite electrode. The user measures current at 4.6 volts across an 8.7 cm diameter dish filled with 20 mL of TSB media, obtaining a current of 2.8 mA at a 1 cm probe distance. The formula for current density (J) is established as J = I / A, where A is the area. The user seeks clarification on how to calculate the area for current density given the specific dimensions and probe distances.

PREREQUISITES
  • Understanding of current density and its formula (J = I / A)
  • Basic knowledge of electrical measurements (voltage, current)
  • Familiarity with geometry of circles for area calculations
  • Concept of resistivity in conductive liquids
NEXT STEPS
  • Research how to calculate the area of a circle and apply it to current density calculations
  • Learn about the relationship between resistivity and current density in conductive media
  • Explore methods for measuring resistance in liquid-filled tubes
  • Investigate the effects of probe distance on current measurements in liquid environments
USEFUL FOR

Electrochemists, physics students, and researchers involved in experimental setups measuring current in conductive liquids will benefit from this discussion.

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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