1. Electrostatics

2. Electrostatics
The branch of science dealing with static charges and their electric fields
The Greek word for amber, ήλεκτρον electron, was the source of the word 'electricity'

3. A little history
The science of electricity has its roots in observation, known in 600 BC that a piece of amber rubbed with animal fur would attract straw, feathers
Thales of Miletos (Greece) in credited with this discovery

4. A quick review of the atom
positively
negatively
Electrons
Every atom has a ______ charged nucleus surrounded by ____ charged electrons.
_______ move in and out of fixed pathways around the nucleus

5. Charges
Two kinds: positive and negative (terms coined by Benjamin Franklin)
Like charges ________
Unlike charges ______
repel
attract

6. Static Electricity

7. What is amber?
Amber is the fossilized form of tree resin…not the same as sap.
Resin is similar to our scabs. It flows out of the tree to plug a hole.

8. The Leyden Jar
Progress quickened after the Leyden jar was invented in 1745
The Leyden jar stored electricity and therefore could be studied at length

9. Benjamin Franklin
1752
By tying a key onto a kite string during a storm, Ben Franklin , proved that static electricity and lightning were the same.

10. The Battery
A new interest in current began with the invention of the battery. Luigi Galvani had noticed (1786) that a discharge of static electricity made a frog's leg jerk.
Galvani thought the leg supplied electricity, but Alessandro Volta thought otherwise. He showed that the metal plate and the Leyden jar were different metals and produced a current. He built the voltaic pile, an early type of battery, as proof.

11. Of the 3 types of subatomic particles, which one can move?
Electrons in the (outer, inner) rings or shells of atoms are bound more loosely to the nucleus
Such electrons tend to break free from the nucleus and wander around amongst other nearby atoms
Such electrons are called free electrons

12. Insulators and Conductors
Different materials hold electrons differently.
Insulators don’t let electrons move around within the material freely.
Ex. Cloth, Plastic, Glass, Wood, Rubber
Conductors do let electrons move around within the material freely.
Ex. Metals- Silver, Copper, Aluminum, Gold 12

13. Objects that tend to give up electrons and become positive:
Glass
Fur
Hair
Wool

14. Objects that tend to attract electrons and become negative:
Rubber
Styrofoam

15. What happens to your hair when you rub a balloon on your head?
The balloon, after being rubbed and then pulled away, removes some of the electrons in your hair which give each strand a positive charge. Like charges want to repel and each strand is repelling from the others and “sticking up.” 15

16. Let’s review
Salt and Pepper

17. Let’s review #4
Water and balloon

18. Review If an object is +3 what does that mean?
It has a net charge of +3
Draw your picture
If an object is -2 what does that mean?
It has a net charge of -2

19. Review How can a neutral object become negative? Gains electrons
How can a neutral object become positive?
Loses electrons

20. Charges..symbol is “q” There are several “laws of conservation”; Mass
Energy
Momentum
Angular momentum (spin)
Charge

21. Law of Conservation of Charge
Charges within a closed system may be transferred from one object to another, but charge is neither created nor destroyed.
So how does a battery run out of energy? 21

22. What is a force field?

23. Force Field
Definition- The area that exists around a mass, electric charge or magnet, so that another object will experience a force
/Star-Trek-style-force-field-armour-being-developed- by-military-scientists.html 23

24. Electrostatic Force
This is a non-contact force (like the gravitational force except instead of two masses exerting force on each other the two objects charges exert a force of repulsion or attraction).

25. Electrostatic Force Fields...NOT force at a distance

26. Be glad you are not a cat

28. Coulomb’s Law-formula for electrostatic force
Again this is similar
to the gravitational force…
Fg = GmM r2
Fe = kq1q2 r2
charge (q) is now
responsible for the force
Just like G was a constant so is k.
k is the electrostatic constant
and = 8.99 x 109 N•m2/C2

29. Fe = kq1q2 r2 Fe r2

30. Coulomb’s Law Practice
micro, nano, pico
µ n p
E E E-12
Million billion trillion
Worksheet