1. Electricity

2. Electricity is the flow of electrons…
To understand electricity, we first have to review the structure of matter

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

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

5. Basic Atomic Structure
Nucleus
Center of atom
99% of atomic mass in nucleus
Where the protons and neutrons are found
Electron Cloud (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 freely
N = 3
N = 2
N = 1
Nucleus

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

7. 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 neutral
If more (+) protons, then positively charged
If more (-) electrons, then negatively charged
Overall, objects that are charged have an unequal number of protons and electrons

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

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

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

11. The second balloon also has a negative charge and it pushes away from the first balloon
Same charges repel

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

13. 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

14. Ways of Charging Charging by friction
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

15. Charging by conduction (contact)
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

16. Charging by induction
Bringing a charged object really close to a neutral object BUT not touching it
Overall net charge of neutral object stays zero

17. Exit Ticket: 9-12

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

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

20. 11. 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

21. 12. 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