PHYS 0175 1st Edition Lecture 4Outline of Last Lecture II. Two Point charges in two dimensionsIII. Principle of Linear Superposition of electrostatic forcesIV. Torque problems with electrostatic forcesV. Electric Fielda. Gravity analogyOutline of Current Lecture VI. Electric Field produced by point chargeVII. Electric Field LinesVIII.Electric DipoleCurrent LectureII. Electric Field produced by point chargea. Electric field E=forces per unit chargei. N/Coulombb. E=limit as q-not-0 F0/q0c. Test charge q0 should be<<source chargei. So that the field does not depend on test charged. Electric field is also vectore. Direction of the force vectorf. F=qEi. Direct proportion between force and Electric fieldii. Analogous to force that earth exerts on body1. F=mg -F=qE2. Gravitational field ga. G=GM/r^2 r-hatg. In the region around the point charge spherical symmetryh. E=kq/r^2 r-hati. Direction of field1. Outward of source charge if positive2. Inward of source charge if negativei. kIII. Electric Field Linesa. Not physical realb. Virtual curvei. Tangent to any point matching direction of electric field vector at that pointc. If single point charge- field lines are straighti. Unless affected by another charged particle’s/object’s field/electrostatic forced. Faradaye. If dipole electric field lines will curvef. Electric field lines do not have equal magnitudeg. Charges generally do not move along electric field linesh. Electric field lines can never crossi. Will always be uniquely definedi. Instantaneous acceleration of point charge put in field is tangent to field line at that pointj. Will also curve if there is any interaction between two point chargesi. Opposite signscurve towardsii. Same signs curves awayIV. Electric Dipolea. Two point chargesi. Equal in magnitudeii. Opposite in magnitudeiii. Close enough in space to
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