1. Electrostatics

2. Do Now
In your notes: Draw an atom of either Helium, Lithium, or Carbon Label all the parts of your atom.
Feel free to use your
phone for some research!

3. The first scientist to study these phenomena was Benjamin Franklin (1706-1790).
Franklin called this property gained by rubbed objects electric charge, and called the phenomenon charging by friction.
He spent a large amount of his fortune purchasing exotic materials, such as silk, to determine several overarching patterns.

4. amber
Ben Franklin chose to call an amber rod negatively charged after it was rubbed with fur, and called the fur positively charged.
fur
This was an arbitrary choice, but formed the basis for
the naming convention still used today.

5. If we assume the Tube becomes negative when rubbed with fur, figure out the charge of all the objects from your lab: + or -
Foam Tube
Fur

6. Review of Charge Charge (Q or q): Fundamental unit of Electricity
Two Types:
Positive and Negative
Source of Charge:
Protons (+), Electrons (-)

7. Charges Exert Forces on Each Other
Like Charges Repel and Opposite Charges Attract
*The closer the charges are, the stronger the force

8. How do Atoms Become Charged?
To become negative, an atom can gain an electron
To become positive, an atom can lose an electron

9. How do Atoms Become Charged?
Protons are never transferred since they are locked in the nucleus!
The only way for objects to become charged is by transferring electrons.

10. Types of Materials Conductors Insulators
outer electrons free to move throughout material
Ex: metals
Insulators
electrons tightly bound to atoms
Ex: plastic, rubber, glass

11. Methods of Charging
What has happened to cause the dog’s hairs to behave the way
they do after the dog is rubbed with the blanket?

12. Methods of Charging
Charging by Friction – 2 uncharged materials are rubbed against each other
electrons transfer from one material to another due to atoms of one material “pulling” electrons more strongly than the other
Objects end with OPPOSITE CHARGE (equal amounts)

13. Methods of Charging
Charging by Contact – touch a charged object to uncharged object
Electrons move one object to another
Objects end with same charge

14. If you touch the objects with the charged rod, what will happen?
Insulator
Conductor
foam
Electrons from the rod are deposited on the objects.
On an insulator the electrons stay put
On an conductor the electrons repel and spread out to the very edge

15. If you touch the objects with the charged rod, what will happen?
Metal Sphere
foam
Electrons from the objects are attracted to the foam (making the rod less +)
Electrons from the entire sphere are attracted to the foam, leaving whole sphere +
In an insulator, only nearby atoms loose electrons and become +

16. Charging by Polarization
Charging by Polarization– bring a charged object NEAR a neutral object
Separates the charges in the neutral object by moving the electrons
Object still has a net charge of 0

17. What if you bring the charged foam near an insulator ?
The charged object repels/attracts the electron clouds – either bringing them closer or farther. This causes the attraction to be stronger than the repulsion!
Figure 14.2

18. What if you bring the charged foam near water?
Water molecules are already polarized! So they turn to put the H+ side toward the negative object!
foam
Figure 14.2

19. Grounding
Grounding – Connecting an object to the ground (the Earth) to avoid build up of charge
Any excess electrons will flow into the ground
Any lack of electrons will be replaced by electrons from the ground.

20. Charging by Induction
A way to charge a neutral conductor using BOTH polarization and grounding

21. Charging by Induction (Conductors)
Charged object brought near an uncharged conductor
Separation of charge develops
Negative Charge leaves the conductor by grounding the conductor
Ground is removed and the conductor now has a net positive charge

22. Charging Two Spheres By Induction:
Bring a Charged object near the spheres
Separate the spheres while the charged object is still nearby.
The spheres end with opposite charge

23. Polarization Grounding Induction Charging By Friction
Charging By Contact
Induction

24. Van de Graaff Generator
Electrons transferred by belt to the metal conducting sphere where they spread out

25. Lightning
The negative side of a raincloud can induce a positive charge on the ground
Lightning occurs when so much charge builds up, that air is turned into a conductor
Lightning: The huge flow of electricity excites atoms causing them to emit huge amounts of light
Thunder: The electricity rapidly heats the air, making it expand quickly, sending out a shock wave of sound

26. Lightning

27. Lightning Rods
Invented by Benjamin Franklin