Nernst Single Ion Gradient Term Tool

Description

Return a single-ion equilibrium potential.

Membrane electrical quantities distinguish total from area-specific properties, concentration ratios from activities and single-ion from multi-ion models. Local capacitance, current or potential terms require compatible sign, valence, temperature and unit conventions without themselves validating a biological membrane.

Return a single-ion equilibrium potential.

When to use this tool

Use Nernst Single Ion Gradient Term when evaluating the stated membrane, ionic or area-basis term.

How to use the tool and how it works

Enter outside, inside, valence, gasConstant, temperatureK, faraday. Use the units and conventions below.
Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
Read potentialVolts. Use the output convention below.

Return a single-ion equilibrium potential. Require positive outside/inside concentrations, R, temperatureK and faraday, and nonzero signed whole valence; potential = R*T*ln(outside/inside)/(valence*F), using log1p near equality.^[1]

The single-ion Nernst potential balances chemical and electrical driving forces. Its concentration ratio requires the intended inside/outside and signed-valence convention.^[2]

Input field	Meaning and units	Accepted input
outside	Outside	Required. Finite number; strictly above 0.
inside	Inside	Required. Finite number; strictly above 0.
valence	Signed nonzero whole ion-charge count; fractional valence is rejected by the field schema.	Required. Safe integer.
gasConstant	Gas Constant	Required. Finite number; strictly above 0.
temperatureK	Temperature K	Required. Finite number; strictly above 0.
faraday	Faraday	Required. Finite number; strictly above 0.

Output field	Interpretation	Returned shape
potentialVolts	Inside-minus-outside single-ion equilibrium voltage for SI molar R and F.	Required. Finite number.

json

{
  "input": {
    "outside": 10,
    "inside": 1,
    "valence": 1,
    "gasConstant": 8,
    "temperatureK": 300,
    "faraday": 96000
  },
  "output": {
    "potentialVolts": 0.057564627324851146
  }
}

Limitations and assumptions

Concentrations need compatible activity assumptions; valence is a nonzero signed whole number, and membrane physiology or a multi-ion potential is not assessed.
Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.

Alternative or Complementary methods

Use verified concentrations, activities, geometry and electrical calibration with the appropriate complete membrane/channel model for physiological interpretation.

References

Calculation and input contract: biophysics/nernst-single-ion-gradient-term — tool.io
Cellular Neurophysiology: equilibrium potential — Stony Brook University

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