Coulomb's Law: It refers to forces that are exerted between point electric charges, that have:
, given by the equation: F=kQq/r2 - Direction, that of the line which connects the charges (centrals) -Sign,
attractive for opposite charges, repulsive for same charges - And depend on the medium where the charges are .


vector of force


On the left figure you see a charge in the center, and a test (black) charge, q=10-9C. If you move the test charge with the mouse, you will notice on the right figure, the force exerted by the central charge on the test charge. You can change the central charge or even show the vector of the force.
Question: Can you use the figures to realize whether the force is
atractive or repulsive;
Exercise: Can you calculate the strength of the central charge?
(hint: drag the test charge to a distance eg. 1m,count the force on the figure and calculate the central charge)