Hopkinsons law

electronics/hopkinson's_law.py

@@ -0,0 +1,39 @@
+#https://en.wikipedia.org/wiki/Magnetic_circuit#Hopkinson's_law
+from __future__ import annotations
+def hopkinsons_law(magnetomotive_force:float, current:float, reluctance:float) -> dict[str, float]:
+    """
+    Apply Hopkinson's Law, on any two given electrical values, which can be magnetomotive force, current,
+    and reluctance, and then in a Python dict return name/value pair of the zero value.
+
+    >>> hopkinsons_law(magnetomotive_force=10, reluctance=5, current=0)
+    {'current': 2.0}
+    >>> hopkinsons_law(magnetomotive_force=0, current=0, reluctance=10)
+    Traceback (most recent call last):
+      ...
+    ValueError: One and only one argument must be 0
+    >>> hopkinsons_law(magnetomotive_force=0, current=1, reluctance=-2)
+    Traceback (most recent call last):
+      ...
+    ValueError: Reluctance cannot be negative
+    >>> hopkinsons_law(reluctance=0, magnetomotive_force=-10, current=1)
+    {'reluctance': -10.0}
+    >>> hopkinsons_law(magnetomotive_force=0, current=-1.5, reluctance=2)
+    {'magnetomotive_force': -3.0}
+    """
+    if (magnetomotive_force, current, reluctance).count(0) != 1:
+        raise ValueError("One and only one argument must be 0")
+    if reluctance < 0:
+        raise ValueError("Reluctance cannot be negative")
+    if magnetomotive_force == 0:
+        return {"magnetomotive_force": float(current * reluctance)}
+    elif current == 0:
+        return {"current": magnetomotive_force / reluctance}
+    elif reluctance == 0:
+        return {"reluctance": magnetomotive_force / current}
+    else:
+        raise ValueError("Exactly one argument must be 0")
+
+
+if __name__ == "__main__":
+    import doctest
+    doctest.testmod()