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??
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