Coulomb's law

We already know that two similar charges attract each other and the two are not similar charges will repel. When it was junior class IX, knowledge is not enough. We also need to know how large a force of attraction and repulsion how-reject.

Charles Augustin de Coulomb, found an association between electric force with the charges and the distance between the charge. This relationship is known as Coulomb's law.

"The magnitude of the force of attraction and repulsion is proportional to the respective charge and inversely proportional to the square of the distance of the two charges."


The force of attraction or repulsion reject is called the Coulomb force or electric force.

Now let's peel this carefully Coulomb's law:
a. The force of attraction or repulsion is proportional to the charge of each

Example:
Two charges each + Q + 2Q and separated by d electric force experienced by F. How big style if each charge to +3 Q and +4 Q?
Completion
From the above can be made about the following diagram.
clip_image001
Because the magnitude of the Coulomb force F is proportional to the charge-charge, it can be written
clip_image002
Consider the following diagram.
clip_image003
It appears that, when charge-charge becomes greater then the Coulomb force is also greater.

b. The magnitude of the Coulomb force is inversely proportional to the square of the distance the two charges
When two separate charges farther away, of course, the influence of the two will be smaller. More tiny, but it is not simply inversely proportional to the square distance of both.

Example:
Two charges each + QC + QC and separated by d Coulomb force experienced by F. How repulsive force-resist, when charge-charge distance to 2d?
clip_image004
Completion
The magnitude of the Coulomb force is inversely proportional to the square of the distance of the two charges, so that the force Couomb F 'it becomes:
The following diagram clip_image006Perhatikan

clip_image007


So, when the distance of the two charges to be 2 times larger, the style Coulombnya ¼ times the force of the original, when the distance to 3 times, then the force Coulombnya to 1/9 times its original style and so on.

Exercise:
1. Two charges each + 2Q and 3Q + d separated by an electric force experienced by F. If the load each into +6 +4 Q and Q,
a. Draw a diagram?
b. How Coulombnya style now?

2. Two charges each + QC + QC and separated by d Coulomb force experienced by F. When the distance between the two cargo into ½ d,
a. Draw a diagram?
b. How Coulombnya style now?

Coulomb's law formula
From the sound of Coulomb's law, which is "the force of attraction and repulsion is proportional to the respective charge and inversely proportional to the square of the distance of the two charges", it can be formulated:
clip_image009
F = magnitude of the Coulomb force (N)
Q1, 2 = charge of 1 and 2 (C)
r = distance between the two charges (m)
k = 9109 N m2/C2

Example:
Two charges each 2μ + 3μ + C and C, separated by 2 cm. If k = 9109 N m2/C2, how much repulsion-reject?
Completion
Given:
k == 9109 N m2/C2
Q1 = 2μ + C = 2106 C
Q2 = 3μ + C = 3106 C
r = 2 cm = 2.10-2 m
Asked: F?
Answer:
clip_image011
= Clip_image013
= Clip_image015

= 13.5. 109-6-6 - (-4)
= 13.5. 101
= 135 N