1. 1. You will need a calculator, your journal, and something to write with If you did NOT finish your notes & questions yesterday, you have until Monday (you’re welcome) Open to the next blank page (leave space to finish yesterday’s if needed) and set up Cornell Notes: Page: 31 Date: Title: Coulomb’s Law Essential Question: How is electrical force between charges calculated?

2. ELEMENTARY Charge: the charge on a single electron
e = 1.6 x C
units for charge are coulombs (C)

3. There are two types of charge:
Positive: a shortage of electrons
Negative: an excess of electrons
Conservation of charge: charges are not created or destroyed, only transferred

4. Electric Forces “like” charges repel + “unlike” charges attract + - F

5. Coulomb’s Law gives the electric force between two point charges.
Inverse Square
Law
k = Coulomb’s Constant = 9.0x109 Nm2/C2
q1 = charge on mass 1
q2 = charge on mass 2
d = the distance between the two charges
Electric force is much stronger than gravitational force on a molecular level.

6. How strong is electrical force?
If 1 negative coulomb were 1 meter away from 1 positive coulomb the force would be 9 billion newtons!
Yes, 9,000,000,000 N!
This is how strong the forces are that hold molecules (and you) together.

7. If d is doubled, then F is : ¼ F
Proportionality Review
Two charges are separated by a distance d and have a force F on each other. q1 q2 d F
If d is doubled, then F is :
¼ F
If q1 is doubled, then F is : 2F
If q1 and q2 are doubled and d is halved, then F is :
16F

8. 1. Determine the magnitude and direction of the electrostatic force on charge 1 if it is 0.20 m away from charge 2.
-4.0 μC
6.0 μC
= -5.4 N…so magnitude and direction of force on charge 1 is 5.4 N RIGHT

9. μC = x10-6 So 3.0 μC = 3.0x10-6 C nC = x10-9 So 3.0 nC = 3.0x10-9 C
k = 9x109 Nm2/C2
μC = x10-6
So 3.0 μC = 3.0x10-6 C
nC = x10-9
So 3.0 nC = 3.0x10-9 C