1. Electrostatics Ch 32 & 33

2. Basic Concept In Mechanics, the basic property of matter is Mass.
In Electricity, the basic property is Charge.

3. Basic Units Compare Smallest Possible Unit Practical Unit US Currency
Penny
$0.01 = 1/100th of a dollar
Dollar
$1 = 100 Pennies
Electric
Charge
Elementary Charge (1e)
electron or proton
1e = 1.6 x 10-19C
Coulomb
1C = 6.25 x 1018e

4. Examples
How many electrons are on a conductor if it has a charge of -4 x C?
250 electrons
What charge will 120 protons have?
1.92 x C

5. Example
Why is it not possible for any object to have a charge of 8 x C?
Electrons (or protons) cannot be broken down into smaller pieces.

6. Movement of Charge Conductors Insulators Electrons are free to move
Most metals
Insulators
Electrons are not free to move

7. Basic Concept
Opposite Charges Attract
Like Charges Repel + - - - + +

8. Movement of Charge Grounding Examples
Charges on an object will try to move away from like charges or towards opposite charges
Examples
Lightning, Static electricity

9. Charging by Contact
When 2 conductors of unequal charges touch, the electrons will move to balance out the charge, leaving both conductors with the same charge

10. Charging by Induction
If a charged object is brought near a conducting surface, even without physical contact, electrons will move in the conducting surface.
Read 32.6

11. Charging by Induction

13. Review Gravitational Force What factors affect gravitational force?
Size of each mass
Distance of separation

14. Electrostatic Force
What factors will affect the amount of attraction or repulsion?
Size of each charge
Distance of separation

15. Coulomb’s Law k = Electrostatic constant, 8.99 x 109 Nm2/C2
q = charge (C)
r = distance separating the center of each charge (m)

17. Electric Fields
Electric Field is a region around a charged object through which a force is exerted on any other charged particle.
Electric Field Lines are imaginary lines drawn to show electric field

18. - Electric Field Lines + Lines are not real Positive  Negative
Can not cross
Closer lines mean stronger field - +

19. Electric Fields Parallel Plates
Electric Field is uniform between plates

20. Electric Field Strength, E
Force per charge
Amount of force felt by a charge
Vector
E (N/C)
Fe (N)
q (C)