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 concepts Charge Force Electron Proton Friction Conduction Induction Sheilding Grounding

The 4 Fundamental Forces Strong 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 Electricity Electrostatics 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 Atom Helium Atom Neutron -Negative Charge ElectronProton -Positive Charge Nucleus 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!!

Ions Most 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 Atoms Neutral Atom Positive Ion Lost an electron so it has a net positive charge

Charged Atoms Neutral 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?

Conduction Conduction (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?

Induction Induction: Bringing a charged object near a neutral object to induce a dipole in the neutral object.  NO TRANSFER OF CHARGE!!!!!

Induction Before:

Induction Induce an “Electric Dipole” Also called polarization The negative charges move away from the negative sphere. REMEMER, the protons don’t move!

Induction Induced charge in both blocks when we separate them Positive BlockNegative Block

Second Example What 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 Objects Using 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 Fields The space around every electrical charge Has both magnitude and direction, a vector quantity Exploring Electrical Fields

Lightning Lightning on Science Joy Wagon