1. Law of electric charges

2. What is an electric charge?

4. Law of electric charges
Opposite charges attract
Similar charges repel each other
Charged objects attract neutral objects

5. Plasma
One of four states of matter – solid, liquid, gas, plasma

6. Charging by friction
Charges (electrons) are transferred when two objects are rubbed together
Based on electronegativity (the ability to attract electrons) which depends on atomic radii and # of protons

7. Charging by contact Charged when objects touch
Electrons repel each other. If there are an excess of electrons, they will push each other off the materials (assuming they are allowed to flow)

8. Charging by Induction
Charge is created through a repulsion between charged objects

9. Law of conservation of charge
What do you think this means? (How many law of conservation of _________ do you know of?)
The total charge (the difference between the amounts of negative and positive charges) within an isolated system is conserved

10. Charge q = ne q – Net Charge (C - Coulombs)
n – Number of excess charges (electrons or protons)
e = x C/charge
If we have protons, charge is positive
If we have electrons, charge is negative

11. Coulomb’s Law 𝐹 𝑒 = 𝑘 𝑞 1 𝑞 2 𝑟 2 Fe – Electric Force (N)
𝐹 𝑒 = 𝑘 𝑞 1 𝑞 2 𝑟 2
Where,
Fe – Electric Force (N)
q1, q2 – Electric Charge (C)
r – Distance between centres (m)
k = 9.0 x 109 Nm2/C2
K is dependent on medium

12. What are the similarities and differences between electric and gravitational fields?

13. Example
The electrostatic force between two small charged objects is 7.0x10-6 N.
A) Calculate the force if the distance between charges is tripled.
B) Calculate the force if the charge on one object is halved while the other is increased by four times.
C) Calculate the force if both a and b occur

14. Example
Charge sphere X and Y are in a fixed position and have charges as shown below:
Calculate the net force on Z.
d= 40.0cm
d= 15.0cm
qX = 5.5x10-7C
qY = -3.4x10-8C
qZ = 8.3x10-7C

15. Example Calculate the net force on sphere # 1. d= 50.0cm q1 = 4.0µC