phys104 final sheet

phys104 final sheet - 10 Electric charge is present in many...

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Unformatted text preview: 10: Electric charge is present in many of the subatomic particles from which matter is constructed, and these particles incorporate their charges into almost everything. Electrostatic forces – the pos and neg forces btw stationary electric charges. Atom contains nucleus containing positively charged protons and uncharged neutrons, surrounded by cloud of negatively charged electrons. Net electric charge – the sum of all its pos and neg amounts of charge. Coulumns law – when 2 clouds with large opposite charges approach, expect lightning. The magnitude of the electrostatic forces btw the 2 objects = coulomb constant*charge1*charge2 / (distance btw charges)^2. Charge transfer – has to do with chemical potential energy, which is the energy stored in the chemical forces that bind together a material’s atoms and electrons. Elementary unit of electric charge – 1.6*10^-19. Electrostatic potential energy – whenever opposite charges have been pulled apart or like charges r pushed together. Voltage – the electrostatic potential energy available per unit of electric charge at a given location. SI unit – joule-per-coloumb,V. static electricity – when clothes tumble in the dryer, contact btw dissimilar materials transfers negatively charged electrons from 1 thing to another. As a result of this constant charging effect, the various garments acquire net charges, some pos and others neg. when the clothes are separated, the work done in pulling them apart becomes electrostatic potential energy and the clothes develop high voltages, which can also occur when you walk across a carpet or drive ur car along the road. Such high voltages push charges into the air as leaks and sparks. You can control static charging with the help of conducting materials: allowing charge to move spontaneously from hi voltage to low voltage prevents large quantities of separated charge from accumulating so that hi voltages cant develop. Electrical conductors – materials like metals that permit free charge movement. Electrical insulators – prevent free charge movement, like plastic, hair, rubber. Photoconductor – a normally insulating material that becomes a conductor while exposed to light. Corona discharge – the copier’s charge sprayer, which is a spark that forms in the air near a needle or fine wire that’s maintained at high voltage. Discharge – a flow of electric charge through a gas(like air). Force = charge*electric field (charged lint accelerates quickly in a region full of static electricity. The SI unit of electric field is the Newton-per- coulomb. With its charges at equilibrium, a homogenous conducting object has a single uniform voltage and the net charge anywhere in its interior is zero. Electric field = Voltage gradient = voltage drop/distance . Copier – the photoconductor is precoated with charge by passing it near a corona discharge, an optical image of the original document is projected onto the charged photoconductor, wherever light hits the photoconductor, the surface charge escapes, then there is a charge image on the photoconductor, then tiny black toner...
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phys104 final sheet - 10 Electric charge is present in many...

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