L01_Electrostatics - Electrostatics Introduction In the...

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Electrostatics Introduction In the first semester of this two-part course, we learned about Newton’s three laws and the gravitation force. These are the backbone of what is called Classical Mechanics. In the second part of this course we begin the discussion of electric forces. Electric forces were studied scientifically for the first time by Benjamin Franklin (1706-1790). He observed that rubbing different materials on other materials caused attractive and repulsive forces to develop. It was later shown by Robert Millikan (1868-1953) that charge always changes by multiples of a fundamental charge, e . This charge is the same magnitude as that of the charge of an electron and a proton. By definition the proton is given a positive sign and the electron a negative. In this lab we will observe the same attractive and repulsive forces observed by Franklin. These forces will be due to the electric force generated by conductively charging objects. In the last part of this lab we will build a Van de Graaff generator. This will use conduction to generate large voltages. Theory Some materials allow electrons to be loosely bound to them. These electrons can act as ‘free’ charges on the surface of the material. Such material is called a conductor. Other materials have all the electrons tightly bound to them. This prevents electrons from freely moving along them. Such materials are called insulators. When a material is rubbed against another material or placed in a close proximity of the other material, if the force by which the electrons are bound to the materials are different, it is possible for electrons to move from one material to the other. When that happens, the material that gains electrons becomes negatively charged. The material that looses the electrons becomes positively charged. Thus the two objects become charged carrying opposite but equal charges. Procedure The construction and pictures of this Van de Graaff generator were taken from http://scitoys.com/scitoys/scitoys/electro/electro6.htm a copy is provided at http://physci.kennesaw.edu/labs/vdg.htm Items needed : An empty soda can A small nail A rubber band, ¼ inch by 3 or 4 inches A 5x20 millimeter glass tube A small DC motor (such as Radio Shack #273-223) A battery clip (Radio Shack #270-324) and a battery holder (Radio Shack #270-382) A Styrofoam cup (a paper cup will also work) Two 6 inch long stranded electrical wires (such as from an extension cord)
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This note was uploaded on 02/09/2011 for the course PHYS 1112L taught by Professor Adler during the Summer '10 term at Kennesaw.

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L01_Electrostatics - Electrostatics Introduction In the...

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