Definition
A non-inductive resistor wound with two parallel wires carrying current in opposite directions, so that the magnetic fields produced by the two windings cancel each other out. The result is a resistor that provides resistance without acting as an inductor.
Plain English
A resistor built with two side-by-side wires running current in opposite directions. Because the two magnetic fields cancel, it slows current the way a normal resistor does but without behaving like a coil.
Context Anchor
Seen in aircraft electrical, radio, and instrument circuit discussions where a resistor must not disturb a changing signal or current.
Derivation
From the Latin 'bi-' meaning two and 'filum' meaning thread or wire. So 'bifilar' literally means 'two-wire.' The name describes how the resistor is constructed: with two wires wound together rather than one.
Why Pilots Care
Prevents magnetic interference that could distort readings in sensitive avionics and instruments.
Analogy
It is like two people pulling on opposite sides of the same rope with equal force: the pulls are still there, but they cancel each other’s outside effect.
Intuition Check
Do not read bifiliar as just “a resistor with two wires attached.” The key point is that the two wound strands are arranged so their magnetic effects cancel.
Example Sentence 1
The technician installed a bifilar resistor in the circuit to avoid the unwanted magnetic effects a standard wire-wound resistor would have caused.
Example Sentence 2
During preflight, the mechanic checked the bifilar resistor in the turn coordinator because an inductive component had caused erratic needle movement.