lecture-01-12-11

# lecture-01-12-11 - Physics 181 To dos:! 1. Register online...

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Physics 181 To dos: 1. Register online on classesv2 2. If pretty sure of taking class, you need a clicker! Get a clicker from Bass library Register the clicker on classesv2 under 3.3. Read Ch. 22 for Fri. Jan. 14 4. Take “Beginning of term survey” on classesv2 First online & written homeworks due Wed. Jan 19

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Last time We talked about electric charges and forces (Ch. 21) • Electric charge is quantized (comes in discrete units) • Electric charge is conserved • Like charges repel, opposites attract • In an insulator, no mobile charges • In a conductor, charges are mobile (electrons) and quickly distribute over the surface of the conductor • Inter-charge forces decrease with distance • Connecting a charged body to a very large conductor will discharge it: essentially all the charge will Fow to the big conductor (reservoir). This is how grounding works • Electric forces can cause polarization: + and – charges will move in opposite directions. Can give rise to forces as well.
Metal sphere A has charge -4. Metal sphere B has charge +2. You make them touch, then separate them. Now A has charge ___ & B has charge ___. 1. 0 ; 0 2. -2 ; -2 3. -2 ; +2 4. -1 ; -1 5. -1 ; +1 6. -2 ; +1

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Polarization Neutral objects can feel attractive electric forces (polarization) : when an external charged body is brought close, charges in neutral object redistribute/shift about to bring opposite charge close to external body. Conductors: this can be quite strong as the mobile electrons can redistribute efficiently pink flamingo + coke can demo
Polarization 2 Insulators: weaker effect; electrons and nuclei polarize (shift slightly) in response to external charges, create dipoles to external body for net attractive force.

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Polarization 3
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## This note was uploaded on 08/12/2011 for the course MATH 118 taught by Professor Jayadevathreya during the Spring '08 term at Yale.

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lecture-01-12-11 - Physics 181 To dos:! 1. Register online...

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