158-ES1 and ES2 Intro rev 3

158-ES1 and ES2 Intro rev 3 - ES1/ES2 Electrostatics In...

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ES1/ES2 Electrostatics In this lab you will explore several aspects of electrostatics such as charging by induction, distribution of charges on conductors etc.

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158-ES1 and ES2: Electrostatics As you learned in lecture, electrostatics is the study of static charge distributions. In order to study a thing, it must be possible to measure it, and it is very difficult to measure charge directly. Capacitor: A device that stores charge, and the amount of charge is related to the potential difference between the onductors as given by: q CV C: Capacitance-For a given set of materials (conductors and conductors as given by: dielectrics) depends only on the arrangement of the materials. If we have the ability to sample the charges in a distribution and then put those charges on a capacitor, we can then measure the voltage. From that voltage, we can deduce the charge. (page 2) 1) How to sample charge? 2) Where to put charge sample for measurement?
Charge Sampling + + + + + + + 1000 V + he proof plane is an Al disc on a non onducting handle The proof plane is an Al disc on a non-conducting handle. If you touch it to a charged object, it will pick up an amount of charge proportional to the amount of charge on the object around the point of contact, allowing you to move those charges to our capacitor. This solves our sampling problem. (page 3)

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electrometer Proof lane Charge Measuring - + + pail shield plane The capacitor we use is known as a Faraday Pail. It consists of an inner ylinder (the pail) and an outer cylinder + - + + + - - - - - - + + ground cylinder (the pail) and an outer cylinder (the shield). The tops of the cylinders are open, allowing us to manually eposit charges as required. q deposit charges as required. This solves the problem of measuring our charge sample. The Faraday pail works in the following fashion: 1) Electric field inside a conductor must be 0. ) Placing a charged object into the pail causes the free charges in the pail 2) Placing a charged object into the pail causes the free charges in the pail to re-arrange themselves to make the E = 0 in the pail conductors. ) Additional charges will flow onto or off of the shield (because it is 3) Additional charges will flow onto or off of the shield (because it is grounded) to ensure E is 0 inside that conductor as well.
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This document was uploaded on 11/04/2011 for the course PHY 158 at SUNY Buffalo.

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158-ES1 and ES2 Intro rev 3 - ES1/ES2 Electrostatics In...

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