1. Physics 133 electromagnetism
Electric Charge and Electric Force
MARLON FLORES SACEDON

2. electromagnetism What is electromagnetism?
A branch of physics which involves the study of the electromagnetic force, a type of physical interaction that occurs between electrically charged particles. The electromagnetic force usually shows electromagnetic fields, such as electric fields, magnetic fields, and light.

3. Law of electric charges
Two positive charges or two negative charges repel each other.
2. A positive charge and a negative charge attract each other.
3. Uncharge material is always attracted by a charge material.

4. Coulomb’s law
Coulomb's law, or Coulomb's inverse-square law, is a law of physics describing the electrostatic interaction between electrically charged particles. The law was first published in 1785 by French physicist Charles Augustin de Coulomb and was essential to the development of the theory of electromagnetism.
Coulomb’s torsion balance

5. Coulomb’s law 𝐹=𝑘 𝑞 1 𝑞 2 𝑟 2 𝑞 2 𝐹 12 - 𝐹 21 𝑞 1 + 𝑟 𝐹∝ 𝑞 1 𝑞 2 𝑟 2
𝐹∝ 𝑞 1 𝑞 2 𝑟 2
𝐹= 1 4𝜋 𝜖 𝑜 ∙ 𝑞 1 𝑞 2 𝑟 2
𝐹=𝑘 𝑞 1 𝑞 2 𝑟 2
𝑞 2
𝐹 12
𝐹 21
𝐹 12 +
𝑞 1 =+25𝑛𝐶 -
𝑞 2 =−75𝑛𝐶
𝑟=3.0𝑐𝑚 + 𝑟
Where: 𝑘 is electric constant
𝑞 1 +
𝐹 21
(Coulomb’s law: force between two point charges)
𝑞 1 𝑎𝑛𝑑 𝑞 2 are interacting charges, in 𝐶𝑜𝑢𝑙 𝑜𝑟 𝐶
𝐹 12 =9𝑥 𝑁∙ 𝑚 2 𝐶 𝑛𝐶 −75𝑛𝐶 3𝑐𝑚 2
1 coul = x 109 statC
𝜖 𝑜 =8.854𝑥 10 −12 𝐶 2 𝑁∙ 𝑚 2
+e=1.602𝑥 10 −19 𝐶
𝐹 12 =9𝑥 𝑁∙ 𝑚 2 𝐶 𝑥 10 −9 𝐶 −75𝑥 10 −9 𝐶 3𝑥 10 −2 𝑚 2
Permittivity of free space
Problem: Two point charges, 𝑞 1 =+25𝑛𝐶 and 𝑞 2 =−75𝑛𝐶, are separated by a distance 𝑟=3.0𝑐𝑚. Find the magnitude and direction of the electric force (a) that 𝑞 1 exerts on 𝑞 2 and (b) that 𝑞 2 exerts on 𝑞 1 .
1 4𝜋 𝜖 𝑜 =𝑘=8.988𝑥 𝑁∙ 𝑚 2 𝐶 2
𝐹 12 =− 𝑁 attractive force
𝐹 21 =9𝑥 𝑁∙ 𝑚 2 𝐶 −75𝑥 10 −9 𝐶 +25𝑥 10 −9 𝐶 3𝑥 10 −2 𝑚 2
𝑘=9𝑥 𝑁∙ 𝑚 2 𝐶 2
𝐹 21 =− 𝑁 attractive force
𝑘=1 𝑑𝑦𝑛𝑒∙𝑐 𝑚 2 𝑠𝑡𝑎𝑡𝐶 2

7. Coulomb’s law
Problem
Two point charges are located on the +x-axis of a coordinate system: 𝑞 1 =1.0𝑛𝐶 is at 𝑥=+2.0𝑐𝑚, and 𝑞 2 =−3.0𝑛𝐶 is at 𝑥=+4.0𝑐𝑚. What is the total electric force exerted by 𝑞 1 and 𝑞 2 on a charge 𝑞 3 =5.0 𝑛𝐶 at 𝑥=0?
ANS: 1.125E-4 repulsive, E-5N attractive, E-5N towards -x-axis

8. Problems/ assignment

9. Problems/ assignment

10. Problems/ assignment

11. Problems/ assignment

12. eNd