1. Shocking
You charge a electroscope by grounding it and then bringing a positively charged insulator near the electroscope. Then you break the connection with the ground and move the positive charge away.
What is the charge on the top of the electrocope?

2. Objectives
How do we explain and measure the forces that push the electroscope leaves apart?
Homework: Finish the worksheet!
Short Castle Learning

3. Review Problems
Sheet
Worksheet

4. Electrical Forces
Coulomb’s Law

5. Opposite charges ATTRACT
Electrostatic Force
Same charges REPEL + +
Opposite charges ATTRACT - +

6. Electrostatic Force r q1 q2 Amount of force depends on: Fe r
CHARGE ON EACH OBJECT
DISTANCE BETWEEN OBJECTS
ELECTROSTATIC CONSTANT: k = 8.99 x 109 N·m2/C2 q1 q2 Fe r r

7. Electrostatic vs. Gravitational Force
Consider two electrons that are 1.0 micrometer apart.
Gravitationally ATTRACTED
Electrostatically REPELLED Fe e- e- Fg
r = 1.0 μm
5.54 x N
2.30 x N

8. Example #1
Determine the electrostatic force between an object with a +2.0 coulomb charge and an object with a -2.0 coulomb charge if they are separated by 2.0 meters.
ATTRACTIVE

9. Example #2
Determine the electrostatic force between an object with -2.0 micro-coulombs of charge and an object with -5.0 micro-coulombs of charge if they are separated by 5.0 nanometers.
REPULSIVE

10. End of PRACTICE