What is "torsion balance"

Torsion \Tor"sion\, n. [F., fr. LL. torsio, fr. L. torquere, tortum, to twist. See Torture.]

1. The act of turning or twisting, or the state of being twisted; the twisting or wrenching of a body by the exertion of a lateral force tending to turn one end or part of it about a longitudinal axis, while the other is held fast or turned in the opposite direction.

2. (Mech.) That force with which a thread, wire, or rod of any material, returns, or tends to return, to a state of rest after it has been twisted; torsibility.

   Angle of torsion (of a curve) (Geom.), the indefinitely small angle between two consecutive osculating planes of a curve of double curvature.

   Moment of torsion (Mech.) the moment of a pair of equal and opposite couples which tend to twist a body.

   Torsion balance (Physics.), an instrument for estimating very minute forces, as electric or magnetic attractions and repulsions, by the torsion of a very slender wire or fiber having at its lower extremity a horizontal bar or needle, upon which the forces act.

   Torsion scale, a scale for weighing in which the fulcra of the levers or beams are strained wires or strips acting by torsion.

n. measuring instrument designed to measure small forces by the torsion they exert on a thin wire