Procedure

This experiment consists of four stages and each stage will teach you a new concept.
The experiment was designed in a way, so that you can quickly change the parameters and observe the results. This makes you to have a more clear picture of the concepts.

Start the experiment by clicking on start button on the top of window.

STAGE 1:

In stage 1, we will see the force between two charges q1 and q2, seperated by distance r. Here, you can change the values q1, q2 and r by using sliders provided at the bottom of window. You have to observe the output values provied at the middle of window. Try to reason the observed values. You can pictorially see the variations in the graph provided at the right of window.
So in the graph you should observe the fact that force is inversely proportional to square of the distance. To move on to next stage press next button on the top of window. 

STAGE 2:

In stage 2, the concept is that Force is proportional to product of charges. This you can observe by changing parameters q1 and q2 by using sliders provided at the bottom of window. See the graph whether it was giving the same information to you or not. Also, you can conclude the fact that k remains constant. 

STAGE 3:

In stage 3, observe the k value for free space by varying the charge values. Try to figure it out whether k for free space remains constant or not. See the graph between k for free space and F. 

STAGE 4:

In this stage we see an interesting experiment. Try to add charges n to the screen by clicking mouse anywhere on the screen. Now you can see the resulting force on a charge due to other charges. We use the principle of superposition,
F₃=F₁₃ + F₂₃