TheAlgorithms/Python · error · ValueError

Electron concentration cannot be negative

Error message

Electron concentration cannot be negative

What it means

Thrown by electric_conductivity() when electron_conc < 0 while exactly one argument is 0. Electron concentration is a per-volume count and cannot be negative; the guard runs before the solver branch that divides by (mobility * ELECTRON_CHARGE).

Source

Thrown at electronics/electric_conductivity.py:50

    >>> electric_conductivity(conductivity=50, electron_conc=0, mobility=-10)
    Traceback (most recent call last):
        ...
    ValueError: mobility cannot be negative
    >>> electric_conductivity(conductivity=50, electron_conc=0, mobility=0)
    Traceback (most recent call last):
        ...
    ValueError: You cannot supply more or less than 2 values
    >>> electric_conductivity(conductivity=50, electron_conc=200, mobility=300)
    Traceback (most recent call last):
        ...
    ValueError: You cannot supply more or less than 2 values
    """
    if (conductivity, electron_conc, mobility).count(0) != 1:
        raise ValueError("You cannot supply more or less than 2 values")
    elif conductivity < 0:
        raise ValueError("Conductivity cannot be negative")
    elif electron_conc < 0:
        raise ValueError("Electron concentration cannot be negative")
    elif mobility < 0:
        raise ValueError("mobility cannot be negative")
    elif conductivity == 0:
        return (
            "conductivity",
            mobility * electron_conc * ELECTRON_CHARGE,
        )
    elif electron_conc == 0:
        return (
            "electron_conc",
            conductivity / (mobility * ELECTRON_CHARGE),
        )
    else:
        return (
            "mobility",
            conductivity / (electron_conc * ELECTRON_CHARGE),
        )

View on GitHub (pinned to f5988cc097)

Solutions

1. Pass the magnitude of the electron concentration as a non-negative number.
2. If your codebase signs carriers by polarity, strip the sign at the boundary: abs(n).
3. Mark the unknown with 0 rather than any placeholder value.

Example fix

# before
electric_conductivity(conductivity=50, electron_conc=-200, mobility=0)

# after
electric_conductivity(conductivity=50, electron_conc=abs(carrier_density), mobility=0)

n = abs(carrier_density) if signed_convention else carrier_density
if n < 0:
    raise ValueError("electron_conc must be >= 0")
name, value = electric_conductivity(conductivity, n, mobility)

When it happens

Trigger: electric_conductivity(conductivity=50, electron_conc=-200, mobility=0) — one zero but negative electron concentration.

Common situations: Charge-carrier bookkeeping where electrons were tracked with a negative sign by convention; noisy sensor data; doping calculations with operands swapped (N_D - N_A reversed).

Related errors

• Electron concentration cannot be negative in a semiconductor
• Hole concentration cannot be negative in a semiconductor
• Intrinsic concentration cannot be negative in a semiconducto
• Conductivity cannot be negative
• mobility cannot be negative

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/5fecaf7851320799. Report an issue: GitHub.