Torsion+Balance

//From: Optimusprime113 and physick.wikispaces.com//

==__//Who Created the// //Torsion Balance and Why?//__==


 * The torsion blance experiment was created around 1783 by a geologist named John Michell, he also created the torsion balance apparatus for this experiment but died before the experiment was completed.
 * The scientist Henry Cavendish then recreated created the torsion balance apparatus in 1798 following Michell's design closely.
 * He did this to confirm experimentally that Newton's law of gravitation was true.
 * When he was asked why he was measuring the gravitational constant he said he was "weighing the Earth"
 * it came to be known also as the Cavendish experiment
 * The device did not become widely known untill Charles-Augustin de Coulomb reinvented it and used it to measure electric force.
 * Coulomb discovered that the electric force between objects is inversely proportional to the distance between the objects.

__The Use Of a Torsion Balance__
>
 * The purpose of a torsion balance is to measure very small forces, like the miniscule gravitational attraction between two small items, or small electrostatic forces.
 * Coulomb used the Torsion Balance experiment to create the formula which is discussed in more detail at the page Coulombs Law.
 * [[image:http://www.kentshillphysics.net/Electr4.gif align="left"]]

__How Torsion Balances Work[[image:http://www.haverford.edu/physics-astro/songs/coulomb%20torsion%20balance.gif width="334" height="262" align="right"]]__

 * A basic torsion balance is a horizontal bar suspended from a wire in a glass case. Touching the bar to begin with is a stationary vertical bar that is both on the inside and outside of the glass case.
 * Touching a charged object to the vertical bar will cause both bars to have the same charge causing them to seperate.
 * The amount of seperation that occurs can be used to determine the gravitational force or elctrostatic force exerted between the two bars.
 * The greater the magnitude of gravitational force or charge of the bars, the greater the fibre twists and the greater the angle of rotation is.

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__Why Torsion Balances Work__

 * What causes a torsion balance to seperate is the conduction that occurs between the charged object and the vertical bar which gives the vertical bar a charge which then in turn causes the horizontal bar to get the same charge making them seperate. Then Induction keeps them seperated.

//References//

 * 1) Julian Rubin, (May 3, 2012), []
 * 2) (May 6, 2012), []
 * 3) Science Group, (May 6, 2012), []
 * 4) James E. Ackroyd, Mark Anderson etc., May 6,2012, Pearson Physics Unit II Chapter 4 pg. 205-206
 * 5) Magnet Lab, (May 22, 2012), []