Day 62Topic 7: Charges and Circuits

Mini Lab…BoC…and next class

3rd Quarter5 Full Classes of Topic 7

Q3 Review Day 67 3/25, 3/26

Q3 Exam Day 67 3/27, 3/30

Brunch of Champions Day 68 3/31, 4/1

half day on 4/2? Yeah right; don’t show up because I am not going to be doing important physics that day.

Topic 7: Charges and CircuitsToday: Review of charges,

discussion of basic atomic physics, electric forces.

Leaving here today: Lots of atomic stuff:How charges are quantizedRules of charge interactionsCharge Separation

1st Thing To DoMake a list of all things you know/remember/can deduce about a) the makeup of an atom

b) how the atom and parts act/react in nature

Quick Review:Parts of atom:

How do they interact?

What is Charge?No idea. It’s a property…

Positive or Negative

ProtonsNeutronElectrons

A fundamentalA fundamental charge is:

Charge is a CONSERVED property, which means…

If Neutral…Are there protons or electrons in

the atom/object?

A non-neutral object is Ionized (or an Ion).

Basic Charge RulesLike Charges_____________

Opposite charges_____________

So in the nucleusTell a story of how

the charges wantto move in thenucleus…

There is a gravitational attraction (from the mass property…tiny) that keeps the nucleus together

There is an electrical repulsion (from the charge property…large) that wants to separate the nucleus

There is a Strong Nuclear Force (from the quarks and…., huge) that keeps the nucleus together

Tape It Up!Each group follow my tape

instructions carefully… Label them A (top) and B (bottom)

Explain the charges of A, B and system before and after the ripping. Be detailed, be dramatic.

How do the signs of A and B compare?Before After

How does the amount of charge of A and B compare?Before After

Has the amount of mass and/or the elemental property of A and B changed?

Tape It Up!How do the signs of A and B compare?

Before AfterHow does the amount of charge of A

and B compare?Before After

Charge of system compared to each tape and total, signs, have you changed the physical properties (mass, element) of the tape?

Picture… Drawing TapeLets draw pics before and after,

and use the SNF to describe what was exchanged

Major IdeaThe net charge on each object (Q) is

measured in Coulumbs (c).

Ex: Tape A had a charge of ___________

Those charges felt charges on the tape, and created a net electrical force between them.

This Coulumb Force is the Electric Force FE. Can attract or repel

WaterWatch for a bit

Why did the water attract to both + and -?

POLAR!

The molecule rotated to the attractive part was closer to the rod, and thus had a stronger attraction than the further repulsion.

Now get fur and rod and canCharge up the rod using the furry

part (fluffier is better).

Don’t touch can, bring it close and parallel to the side.

Observe…

Can drawing and Rod…before

Can drawing and Rod…After

Summarize