1. Static Electricity

2. History
• Electron means “amber” in Greek
• Thales of Miletos 600 BC discovered
properties by Greek.
• He rubbed amber (mineral) with cat fur
and attracted feathers.

3. Ben Franklin’s Kite Experiment (1740’s)

4. Benjamin Franklin
• 1740’s lightning experiment
with kite, key and Leyden jar
(stores static electricity).
• Franklin developed the
lightning rod.
• Proposed conservation of
charge.
• Saw electricity as a flowing
fluid and called the flow
direction positive.

6. Law of Charges
• Like charges repel
• Opposite charges attract

7. Law of Conservation of
Electrical Charge
• The net charge of an isolated system
remains constant.

8. Electrical Charge
• Symbol: q
• Unit : Coulomb, C

9. Charge and Mass
of the Electron
• Charge of Electron:
1.6 x 10-19
C (Coulombs)
• Mass of Electron:
9.11 x 10-31
kg.

10. Positively
charged
objects lost
electrons.
Example:
Rubbing a glass rod with silk.
•Rod becomes + (loses electrons)
•Silk becomes - (gains electrons).

11. Negatively charged
objects have gained electrons.
Example: rubbing a rubber rod with fur.
• Rubber Rod: - charged
• Fur: + charged

12. Types of Materials in terms of
Electrical Conductivity
• Conductors (metals)
• Semiconductors (germanium, silicon)
• Insulators (wood, glass, rubber)

13. Electrostatic Charging Methods
• Friction
• Conduction
• Induction

14. Charging by Friction
• The two objects wind up with opposite
charges.

15. Charging by Conduction
(direct contact)
• The objects end up with the same type charge.
• If the charges are equal in size, they share the
charge equally.
http://www.ap.smu.ca/demonstrations/index.php?option=com_content&view=article&id=106&Itemid=85

16. Charging by Induction
• Objects ends up with opposite charge.
• Involves grounding.
http://www.physics.sjsu.edu/becker/physics51/elec_charge.htm

17. Electroscopes are used to test
the charge of an object.

18. When a charged object is
brought near the electroscope,
its leaves spread apart.
http://upload.wikimedia.org/wikipedia/commons/e/ec/Electroscope_showing_induction.png

19. When a charged object touches
an electroscope, the
electroscope is now charged.

20. What was the charge of the
object that touched this
electroscope?

21. Polarization
http://www.csiro.au/helix/sciencemail/activities/WaterBend.html

22. Part II
• Coulomb’s Law

23. Coulomb’s Law
• 1785,Charles Augustin Coulomb
(French scientist)
F = k q1q2
______
d2
• k = 9 x 109
Nm2
/C2
• d (or r): distance between the charges.
•

24. The Direction of the Electrical Force

25. Coulomb’s Law is an Inverse
Square Law
http://web.ncf.ca/ch865/graphics/Coulomb.jpeg