Relics of history

  A capacitor is an electronic device that is used to store electrical energy . It is made up of two conduct ive plates separated by an ins ulating material called a die lect ric . When charged , the capacitor stores energy in the form of an electro static field between the two plates . This stored electrical energy can then be released when needed . One type of capacitor is the electroly tic capacitor . These capac itors are made from two metal plates that are separated by an electroly te solution . This type of capacitor is used in DC circuits and can store a large amount of energy . Another type of capacitor is the ceramic capacitor . Cer amic capac itors are made from layers of ceramic material and are used in high - frequency circuits . They are usually small and can store less energy than electroly tic capac itors but can handle higher volt a...

  A transistor is a semic onductor device used to amplify or switch electronic signals and electrical power . It is composed of semic onductor material with at least three terminals for connection to an external circuit . A voltage or current applied to one pair of the transistor 's terminals controls the current through another pair of terminals . Because the controlled ( output ) power can be much larger than the controlling ( input ) power , the transistor provides amplification of a signal . The history of the transistor dates back to the 1920 s when semic onductor research began . The first trans istors were created in 1947 by William Shock ley , John Bard een , and Walter Br att ain at Bell Labs . They were made from a material called g erman ium . These early trans istors were point - contact trans istors , which were made from two closely spaced met...