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

In summary, the conversation discusses setting up a petri dish filled with TSB media and measuring current at different distances using graphite probes. The question is raised about calculating current density using the known information of current and area. There is also mention of estimating resistivity and considering the path of current in a liquid.
  • #1
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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  • #2
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.
 
  • #3
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
 

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

1. What is the formula for calculating current density in a Petri dish with a 0.7 mm graphite electrode?

The formula for calculating current density is J = I/A, where J is the current density in A/cm2, I is the current in A, and A is the area of the electrode in cm2.

2. How do I measure the current in the Petri dish?

The current can be measured using an ammeter connected in series with the electrode and the power supply. Make sure to set the ammeter to the appropriate range and record the value in amperes (A).

3. What is the area of the graphite electrode in a 0.7 mm Petri dish?

The area of the graphite electrode can be calculated using the formula A = πr2, where A is the area in cm2 and r is the radius of the electrode (0.35 mm in this case).

4. How does the current density change with different electrode sizes?

The current density is directly proportional to the area of the electrode. As the electrode size increases, the current density decreases and vice versa.

5. Can I calculate current density for non-graphite electrodes?

Yes, the formula for current density can be applied to any type of electrode as long as the area is known. Just make sure to use the appropriate units for area (cm2) and current (A).

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