Aditya Abeysinghe Presentations

What is a Van De Graaff generator? A Van De Graaff Generator is an electrostatic generator and a high electric potential accumulator on a hollow metal globe. Van de Graaff generators are described as "constant current" electrostatic devices. When you put a load on a Van de Graaff generator, the current (amperage) remains the same whereas the voltage that varies with the load. A Van de Graaff generator operates by transferring electric charges from a moving belt to a terminal. A typical Van de Graaff generator (labeled) looks like the following: (Photo credit : Wikipedia) Parts of the above generator are as follows: Hollow metallic sphere (with positive charges) The brush (ensures contact between the electrode and the belt) Upper roller (Plexiglass) Side of the belt with positive charges Side of the belt with negative charges Lower roller (metal) Lower electrode (ground) Spherical device with negative charges (used to discharg

A calomel electrode ( popularly called Saturated calomel electrode or SCE) is a based on the reaction between elemental mercury and mercury(I) chloride (calomel).  It is used as a reference electrode in many electrochemical experiments since its electric potential is known. It is also sometimes used in pH calculations and cyclic voltammetry. (Photo credit: dc181.4shared.com) The aqueous phase in contact with the mercury and the mercury(I) chloride (Hg 2 Cl 2 , "calomel") is a saturated solution of potassium chloride in water. In this electrode, the activity of the metal ion is fixed by the solubility of the metal salt. Thus, the half reaction that occurs inside this electrode can be denoted as follows: Hg 2 2+  + 2e   ↔    2Hg    (Note that in the above reaction the left-right arrow represents that this reaction is under equilibrium conditions or that both the forward and the reverse reactions are in equilibrium) Therefore