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## Charge It Up

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**Charge It Up**Session 2 Spring ‘11**Calendar**• Today – Charge overview and some background on the actual FORCES between charges. • Coulomb’s Law Introduction. • Sunday – Brief WebAssign is due. • Monday – MLK Birthday – No Class • Wednesday – Additional Work on Forces • Friday – First Quiz • NOTE: Always bring the current unit and the next unit to class.**Scotch Tape**What’s wrong with this picture?? Two the same! Charge Transfer**Types of Charge**• Positive • Negative • Squiggle**The Atom and Charge**Electron (-e) Weakly Bound in a METAL Charge is QUANTIZED (e) or (-e) Electron (-e) Strongly Bound in an INSULATOR Proton (e) Always Immobile**Van DerGraaf Generator**Charge Transfer**H**OW ? WHY??**Can you charge this metal sphere without touching it??**INDUCTION**SEDUCTION??**ATTRACTION ROLL ! +++++++ EMPTY Coke? Pepsi? Beer? - - - - ++++**Balloon Anybody?**Polarization**Effects**• Charge Transfer • Charge Induction • Charge Polarization • Magic**Is the FORCE with you??**Observation Noted with the tape? The closer the charges are to each other, the bigger the force between them**Coulomb’s Law**• F is a VECTOR • q is a charge measured in “Coulombs” (more soon) • k is a constant ~9x109 Nm2/C2**More on Coulomb**• If the two charges have the same sign, the product of the charges is positive and the force is repulsive • If the two charges have opposite signs, the product of the two charges will be negative and the force will be attractive.**A small spherical insulator of mass 2.00 x 10-2 kg and**charge +0.600 µC is hung by a thin wire of negligible mass. A charge of −0.900 µC is held 0.150 m away from the sphere and directly to the right of it, so the wire makes an angle θ with the vertical. What is the angle? What is the tension? 46.8.296**Start the nextunit**Unit 02 Coulomb’s Law