`E2 - Electric Field·Electrostatic &amp; gravitational force·act at a distance, no direct push or pull conceived by Michael Faraday extends out from every charged object other charges interact with field direction of field determined by motion induced on a positive test charge·Electric Field· · · ·General Physics 2Electric Field1E2 - Electric Field·Coulomb's Law· ·Action-at-a-distance model Charges act directly on one each othercharge &quot; charge·Electric Field· ·!Field model Field acts on chargecharge &quot; field &quot; chargeGeneral Physics 2 Electric Field 2Electric Field·Electric field is a vector expressed in terms of the electric force and the charger r Fe E&quot; qr r Fe = qEr E=! · If Q &gt; 0, E points away from Q·1 q ^ rPC 2 4 &quot;#0 rPC !Electric FieldIf Q &gt; 0, E points away from Q3!General Physics 2Magnitude of Test Charge, q0· The test charge is a conceptual tool to help understand the magnitude and direction of the electric field. · The magnitude of the test charge is VERY small. · The test charge does not affect existing charge distributionGeneral Physics 2 Electric Field 4Electric Field:A proton is released in a uniform electric field, and it experiences an electric force toward the south. What is the direction of the electric field?1. 2. 3. 4.North South East WestElectric Field:An electron is released in a uniform electric field, and it experiences an electric force toward the west. What is the direction of the electric field?1. 2. 3. 4.North South East WestElectric Field:What are the magnitude and direction of the electric force on an electron (e=1.6x10-19 C) in a uniform electric field of strength 2000 N/C that points due east?1. 2. 3. 4.3.2x10-16, east 3.2x10-16, west 8.0x10-23, east 8.0x10-23, westThink-Pair-Share·Calculate the electric field 0.1 m from a 10-6 C charge.General Physics 2Electric Field8Analogy·Electric field is electric force per unit charge. What is the analogous quantity for gravitational force? Derive a mathematical expression for gravitational field. Have you seen this quantity before?General Physics 2Electric Field9Electric Field Lines·Field lines show the magnitude (in a relative way) and the direction of the force felt by a positive test chargeGeneral Physics 2Electric Field10Electric Field Lines (L)·Draw field lines for the following charge distributions-+General Physics 2Electric Field11Electric Field Lines (L)·Draw field lines for the following charge distributions--General Physics 2Electric Field12Superposition·How do you calculate the electric field due to multiple charges? · Calculate the field due to each charge and add them up!r r r r E = E1 + E 2 + E 3 + ...General Physics 2 Electric Field 13Think-Pair-Share (L)Q1 = -1x10-6 C Q2 = 10 x 10-6 C·Two charges, Q1 and Q2, are separated by 100 nm. What is the electric field midway between the charges?General Physics 2Electric Field14Think-Pair-Share (L)Q1 = 1x10-6 C Q2 = 10 x 10-6 C·Two charges, Q1 and Q2, are separated by 100 nm. Where on the line joining Q1 and Q2 is the electric field equal to zero?General Physics 2Electric Field15Electric Field is a Vector· ·What is the net Electric field at point A? What is the net force on a charge Q that is placed at A?General Physics 2Electric Field16Electric Field of a dipole··A dipole is a pair of particles separated by a small distance, equal magnitude and opposite signs The field of a dipole decreases with distance more rapidly than a single chargeGeneral Physics 2Electric Field17A dipole has an electric field··A dipole is electrically neutral, so why does it have a field? The electric field of the near charge is longer than that of the far chargeGeneral Physics 2Electric Field18Field of the dipoleGeneral Physics 2Electric Field19Torque of a dipole·The torque of a dipole in an external electric field·r r v r v v v &quot; dp = d # qE = qd # E = pe # E r r pe \$ qdGeneral Physics 2 Electric Fieldd is the distance displacement vector from &quot;-&quot; to &quot;+&quot;20Water is a dipole·If water is put in an electric field, the water molecules will experience a torque that attempts to twist themGeneral Physics 2Electric Field21LightningInteractions b/w hail and smaller ice crystals transfer e- to hail. They are heavier and sink to base of cloud. Ice Crystals HailThunder: shock wave created by rapid heating of airLight due to e-'s recombining w/ions Path of lightning is about 1 cm in diameterUpward streamers of + ions travels up from ground. Lightning occurs if it meets stepped leader from cloud.e- run away from cloud base, leaving net + charge on ground under cloudLethal Strike·Physiological effects of a direct strike:· · ·stops heart paralyzes muscles internal burns need mouth-to-mouth Side flash or touching struck object Ground current Dead-end upward streamerGeneral Physics 2 Electric Field 23·Heart may restart, but breathing won't··Other types of strikes:· · ·Lightning Rods·Provide path for current to pass directly to ground without passing through building·path of least resistance· ·Diffuse charge build-up Photo from lightning research center in FL·lightning rods may not provide enough protection to homes built on sandy soilGeneral Physics 2 Electric Field 24Lightning Safety· ·Lightning kills ~100 people per year in US Stay inside if possible. Avoid:·showers·much lower resistance when wet· ·phones (cell phones are ok) any electrical appliances avoid tall objects seek low-lying area duck head, crouch pull feet together, run, hop on one foot (ground current) stay in car - Faraday cage (Note: Saturns are not safe!)General Physics 2 Electric Field 25·If outside,· · · · ·Lightning: Physical Characteristics·Voltage·several hundred million volts 1020 electrons in a fraction of a second ~10 kiloamps Good question. We'll get to that soon.·Current· ··So what is a Volt? what is an amp?·General Physics 2Electric Field26Electric Field:The electric field just before a lightning strike points: 1. toward the ground 2. toward the cloud 3. along the groundGroup Problems·E2B.4, E2B.5, E2S.2General Physics 2Electric Field29`

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