1. Coulomb’s Law
Electrostatic Force

2. Charge Q Any amount of charge can be denoted by Q or q
The unit for charge is the Coulomb (C).
One Coulomb is a HUGE amount of charge.

3. Key Facts
The charge on a proton and an electron are EXACTLY THE SAME MAGNITUDE.
Electrons have a negative charge, Protons a positive charge.
The amount of charge on either particle is called the Elementary Charge.

4. Elementary Charge
The Elementary Charge is defined as the amount of charge on one electron or one proton.
e= x10-19C
qproton = x10-19C
qelectron= x10-19C

5. Finding total charge
To find the total amount of charge contained in 1million electrons, simply multiply q of one electron times 1million.
q = (1,000,000)(-1.602x10-19C)= x10-13C
Charges (q) always come in multiples of the Elementary Charge.

6. Charges on Objects
Charge is described at the charge on a single object, NOT how many electrons it has.

7. Coulomb’s Law
Gives the force between two charged objects at any distance. This is called the Electrostatic Force.
Coulomb’s Constant (kc):
kc= 8.99 x 109 N-m2/C2

8. Coulomb’s Law
Formula:

9. Coulomb’s Law
Formula:
Charge on object 1

10. Coulomb’s Law
Formula:
Charge on object 2

11. Coulomb’s Law Formula:
Distance between the two objects. Don’t forget to SQUARE IT!

12. Solving Coulomb’s Law If Felec is negative, the force is ATTRACTIVE.
If Felec is positive, the force is REPULSIVE.

13. Electricity and Gravity
Electricity and Gravity are very similar. Compare the equations for Electrostatic Force and Gravitational Force…

14. Example
A balloon rubbed against denim gains a charge of -8.0 µC (10-6C). What is the electric force between the balloon and the denim when the two are separated by a distance of .05m?