Electricity

Electricity is the To understand electricity, we first have to review the structure of matter

Atomic Size Atom = Comes from Greek word for “uncuttable” or “indivisible” Smallest unit of an element of that element; Building blocks of matter Nucleus Electron Cloud

- Basic Atomic Parts + Sub-atomic Particles : Positively charged (+1) Mass = 1 atomic mass unit (amu) Found in nucleus of atom Neutrally charged (0) Mass = 1 amu Negatively charged (-1) Mass ≈ 0 amu (is extremely small) Found in energy shells outside nucleus of atom + -

Basic Atomic Structure : Center of atom 99% of atomic mass in nucleus Where the protons and neutrons are found (Energy Shells) Regions around nucleus where electrons are found based on how much energy they have Because electrons are not tightly bound in the nucleus, they can move N = 3 N = 2 N = 1 Nucleus

THINK! What are the charged parts of the atom? Which part of the atom moves freely around the nucleus?

Neutral v. Charged Because electrons can move freely: When an atom has a balanced number of positive (+) protons and negative (-) electrons, then the object is If more (+) , then positively charged If more (-) , then negatively charged Overall, objects that are have an unequal number of protons and electrons

THINK! What makes an object positively charged? What makes an object negatively charged? What makes an object neutral?

When electrons move (like when you rub a balloon on your hair or wool), the moves too! In the balloon case, your hair or wool is left with a and the balloon now has extra electrons so it has a charge Your hair or wool and the balloon “stick together” positive-negative/ neutral-negative

What if I charge a second balloon by rubbing it against hair or wool…

The second balloon also has a negative charge and it pushes away from the first balloon

Conductors v. Insulators are materials that electrons can freely flow through Conductors distribute electrons throughout an object Ex. Metals, Water, YOU… are materials that electrons can’t easily move through In insulators electrons get “stuck” in one place Dry air, wood, glass, rubber

THINK! Are electrical conductors/insulators the same or different from heat conductors/insulators? Give an example of a good conductor for electricity and a poor conductor of electricity

Ways of Charging When objects slide past each other One materials gains electrons/ one loses electrons Balloon on head, rubbing your feet on the floor and getting shocked by a doorknob

A charged object comes in contact with a neutral object The charged object “gives” its charge to the neutral object Ex. Touching a charged balloon to neutral bits of paper

Bringing a charged object really close to a neutral object BUT not touching it Overall net charge of neutral object stays zero

Exit Ticket

Which of the following particles has a negative charge? Proton Neutron Electron Atom

Which of the following is not a good conductor of electricity? A. Aluminum B. Glass C. Silver D. Copper

A conductor differs from an insulator in that a conductor…. Has an excess of protons Has an excess of electrons Can become charged and an insulator cannot None of the above

Electrical forces ____. a. can cause objects to only attract each other b. can cause objects to only repel each other c. can cause objects to attract or repel each other d. have no affect on objects