Source: https://guthlabs.ai/docs/instruments/biot-savart-field-of-a-straight-wire-calculator/implementation/

instrument implementation / implementation-contract

# Biot-Savart Field of a Straight Wire Calculator implementation

A source-bound implementation contract for Biot-Savart Field of a Straight Wire Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t5-192

**Effect**: Computation or source lookup only

## Input and validation requirements

The instrument breaks on the exact input r=0 because the formula divides by zero and should return an explicit rejection or undefined result. It is also vulnerable to a factor-of-100 error when a distance is entered without an explicit unit.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "I": 5,
    "I_unit": "A",
    "r": 0.02,
    "r_unit": "m",
    "wire_axis": "+z",
    "current_direction": "+z",
    "observation_side": "+x"
  },
  "expected_outputs": {
    "B_magnitude_T": 0.00005,
    "direction": "+y"
  },
  "working": "B=(μ0 I)/(2πr)=[(4π×10^-7)(5)]/[2π(0.02)] = (20π×10^-7)/(0.04π) = 500×10^-7 = 5×10^-5 T. By the right-hand rule, +z current viewed from the +x side gives +y field."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/biot-savart-field-of-a-straight-wire-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/biot-savart-field-of-a-straight-wire-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/biot-savart-field-of-a-straight-wire-calculator/qualification/>)

## Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

- `VERIFIED_LEDGER.json`

- `evidence-tranche5/tranche5-results.json`