Some Thought Questions:Why do some TVs build up so much dust very quickly?

Why does saran wrap stick to your bowl when it is just plastic and nothing more?

Why doesn’t your cell phone work in some elevators?

Static Electricity

Some upcoming conceptsCharge

Force

Electron

Proton

Friction

Conduction

Induction

Sheilding

Grounding

The 4 Fundamental ForcesStrong Nuclear Force – The force that is involved in holding the nucleus of an atom together

Electromagnetic Force – The force that exists between charged particles

Weak Nuclear Force – The force involved in nuclear decay

Gravity – The force that exists between any two objects that have mass.

Static ElectricityElectrostatics is the part of physics that deals with the interactions between unmoving charges.

But where do we see these forces interacting?

An Electrostatic force is the force that exists between two charged objects.

Static: Unmoving

Electricity: Charges

Static Electricity: Unmoving Charges

Structure of the AtomHelium Atom

Neutron

-Negative ChargeElectron Proton

-Positive ChargeNucleus of Atom

Charge Interaction: Unlike Charges

- +

+-

Opposite Charges Attract

- +- +- +

- -

Charge Interaction: Like Charges

- -Like charges REPEL each other

+ +

+ +

- -- -- -

+ ++ ++ +

Electrostatic Force(Coulomb’s Law)

Coulomb’s Law states that

the stronger a charge is, the stronger the force is between it and other charges, and

the bigger the separation between the charges, the smaller the force.

Is there another force that acts just like Electrostatic Forces?

Universal Gravity

Other then the fact that charges don’t just attract, but repel as well, they work the EXACT same way as masses and gravity!!

IonsMost atoms have an equal amount of protons and electrons. Because of this they are neutral (they have no NET charge)

If an atom has too few electrons, it has a net positive charge

If n atom has too many electrons, it has a net negative charge.

These are called IONS.

Ions are NEVER created by moving or trading protons. The only part of an atom that moves from place to place is an electron.

Charged AtomsNeutral Atom

Positive Ion

++

-

Lost an electron so it has a net positive charge

Charged AtomsNeutral Atom

Negative Ion

++

-

Gained an electron so it has a net negative charge

-

-

How to Charge and Object

Friction: Charging two objects by rubbing them together.

One takes electrons from the other so one becomes positive and one becomes negative

Examples of charging by friction?

ConductionConduction (Contact): Since charges like to spread out, touching a charged object to a neutral or differently charged object will transfer charge.

What are some examples of charging by conduction?

InductionInduction: Bringing a charged object near a neutral object to induce a dipole in the neutral object.

NO TRANSFER OF CHARGE!!!!!

Induction

Before:

InductionInduce an “Electric Dipole”

Also called polarization

The negative charges move away from the negative sphere. REMEMER, the protons don’t move!

InductionInduced charge in both blocks when we separate them

Positive Block Negative Block

Second ExampleWhat will happen if a bring a very positively charged object near another object?

+

++

+

+

+

+ +

Induction

+

++

+

+

+

+ +

The electrons move toward the positive object and a dipole is still formed!

Neutral ObjectsUsing your knowledge about induction and dipoles, how do you think Neutral Objects are affected by charged objects?

They Attract!

Neutral objects are attracted to charged objects

Review of Insulators and Conductors

- In a conductor, electrons will spread out so they are as far apart from each other as possible

- Metals, water with dissolved materials in it

Conductor: Allows Electricity to flow easily

Insulator: Does NOT allow electricity to flow easily

- Glass, rubber, plastic, wood, pure water

How does charge distribute itself on an object?

•Charges spread out as much as they can. (only happens on conductors)

•To make the forces equal everywhere, charges will bunch up at corners.

Charge Distribution

What should you do if a broken power lands on top of your car?

Charge distribution on a car

Shielding

Static charge occupies only the outer surface of a conductor; inside the conductor the electric field is zero.

Electric FieldsThe space around every electrical charge

Has both magnitude and direction, a vector quantity

Exploring Electrical Fields

Lightning

Lightning on Science Joy Wagon