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 chargedOne 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, waterWhat 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?

Charges cannot be created or destroyed, either…they are just transferred.

So: if 1 thing loses electrons, something else gains electrons

Law of Conservation of Charge

How can charges be transferred? 3 Ways:

FrictionConductionInduction

1. Friction – transfer of electrons by rubbing it against another object. Electrons are “wiped” from one object to another.Something that gains electrons becomes negativeSomething that loses electrons becomes positiveEx:

○ 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. ConductionTransfer of electrons by direct contactExample: Static electricity to hands touching

a door knob.

How can charges be transferred?

3. InductionTransfer 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.