Upload
juniper-walton
View
218
Download
0
Tags:
Embed Size (px)
Citation preview
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