What is Electric Charge?  Which particles inside atoms have a charge?  A: Protons (+) Electrons (–)  Charge is a physical property—if an object has a charge, it can lose it.  We think about charges in terms of electrons

Charges  Electrons MOVE  When electrons move from one object to another, we say that both objects are charged One object has a negative charge, and the other has a positive charge

Charges  Charged objects exert a force (a push or a pull) on other charged objects  We call this force the Electric Force: the force of attraction or repulsion on a charged particle that is due to an electric field.

Conductor  A material in which charges can freely move. Conducts electricity!  Examples: metals, pennies, pencil lead, water What other examples can you think of?

Insulators  A material in which charges cannot freely move. Does not conduct electricity! Examples: plastic, wood, paper, eraser ○ What other examples can you think of?

Charges  Law of Electric Charges: Like charges repel (push away) and opposite charges attract

Law of Electric Charge

Law of Conservation of Energy States that… Energy cannot be created or destroyed! Do you remember the MOST important thing that Mrs. Merchant taught you?

CCharges cannot be created or destroyed, either…they are just transferred. SSo: if 1 thing loses electrons, something else gains electrons Law of Conservation of Charge

How can charges be transferred?  3 Ways: Friction Conduction Induction

 1. Friction – transfer of electrons by rubbing it against another object. Electrons are “wiped” from one object to another. Something that gains electrons becomes negative Something that loses electrons becomes positive Ex: ○ Feet on the carpet—become negative ○ Clothes in a dryer—some become (+) and some (-). Dryer sheets are (+), which neutralizes the negative charges. How can charges be transferred?

 2. Conduction Transfer of electrons by direct contact Example: Static electricity to hands touching a door knob. How can charges be transferred?

33. Induction Transfer of electrons due to an electric field without direct contact. Example: Getting close to a charged object and getting a shock.

Socks on the Carpet: Before Charging After Charging Carpet Sock

 1. By which method did the electrons move from the carpet to the girl’s sock? (F, C, or I?)  Friction  2. Which object lost electrons? Which object gained?  Carpet lost electrons, sock gained electrons  Carpet is positive, sock is negative

 3. By which method did electrons travel from her sock to her foot?  Since they are touching, conduction  4. Which one lost and which one gained electrons?  Sock lost electrons, foot gained electrons  Sock became neutral, foot became negative

 5. By which method did the doorknob become positively charged?  Induction—she didn’t touch it!  6. What will the girl feel?  Discharge—AKA Shock!

Electric/Static Discharge  The release of electricity stored in a source  Shock!

 Negative charges become neutral  Electrons transfer until both objects are neutral

 Spark/Shock  Lightning

 Air swirls causing friction to occur  Buildup of charges (electrons)  To restore neutral conditions, electrons must be transferred  Transfer of electrons causes the air to heat up causing light.