PHYS 0970Exam # 1 Study Guide Lectures: 1 - 8Lecture 1 (Jan 5)Introduction to chargeDescribe the types of possible charges. How do opposite charges interact? How do like charges interact? How can charge be created? (friction)What are the origins of electric charge?Lecture 2 (Jan 7) Differences vs conductors and insulatorsInduction vs charging by contactConductors tend to be metals, insulators nonmetals-conductorsfree flow of charge-insulatorscharges cannot move freely, cannot charge by induction-semiconductorsatom:-proton, neutron, electron-in nucleus(proton and neutron)makes up majority of weight-electron orbitalsmakes up majority of space in atom-proton and electron have equal and opposite chargesCoulomb’s lawWhat are the similarities in the equations for gravitational and electrostatic forces?Conservation of chargeWhat does quantization of charge mean?How to neutralize a chargeLecture 3 (Jan 9)Principle of Linear Superpositionadd x and y componentsHow to calculate r-hat-Value must always be 1 with only a direction-direction in unit vector notation or magnitude angle notationi. For a force of F21(force of 2 acting on 1) r-hat=(r1-r2)/r where r is the distance between the two charges, r1 and r2 are distances from the origin(can use vector coordinates i,j,k hatsTorque problems-consider forces at pivot point-clockwise or counterclockwise-rxF-torque on Electric diple is a force produced externally! Torque!=0, but Fnet=0Electric Field produced by dipole vs electric field(and force) acting on a dipoleWhat is necessary to create an electric field? What must be present to detect and electric field?-assume test charge is negligibleLecture 4 (Jan 12) F=qERegion around point charge=spherical symmetryWhat types of charges point inward? What types point outward?-Electric field lines are not physically real!If single point charge-straight electric field lines b/c not affectedif dipole(2 equal and opposite charges near on another)-will curve because their forces act on each other = & opp-lines never crosswhat happens to the field lines of two line charges? To unlike charges?Lecture 5 (Jan 14)Dipole moment p=qdPoints from – to +Torque on dipole and dipole U(potential energy)When is it in stable equilibrium(U=0)? Unstable(U=max)? U=-pEcos(theta)Electric dipole at a distance?Continuous charge distributions(requires integration)-rod-disk-layers-R infinity infinite sheet-ring-ring at a distancewill only need to integrate if these are not standard shapes(ie half a ring, disk etc)units for E?When to use areal charge density vs surface charge densityLecture 6 (Jan 16) Electron oscillating about ringIf the ring is positively charged, will the electron stay at the center?Between two parallel charged platesWhere do the electric fields not cancel?(middle)Does it matter where in the middle?(hint uniform electric field)Acceleration of proton/electron(one plate on top, one on bottom)Analogous to a parabola(except can move up or downwards)x-component of velocity constant, y-cmponent has accelerationuse kinematics equationsLecture 7 (Jan 21) Flux-volume flow rate of chargeCalculating flux itself is not as useful as calculating electric field!Electric field must penetrate surface, if simply glides, then that side has no fluxSI units?Dot productloses directionWhat type of surface makes a guassian(imaginary) surface ideal?Does size or shape matter?Does external charge/flux ever contribute?Surface must be enclosed!Lecture 8 (Jan 23) Goal of guass’ lawto find a surface where E is constant and independent of radius/distance to object of charge, so that we can take it out of the surface integralMay have linear superpositionTake two ie spheres, treated separately-but both must include point P(observer)Find flux of one then add to other with use of the different Gaussian surfacesShell
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