Coulomb’s law
Like charges repel and unlike charges attract. How much difference does distance make?
The electrostatic force between two stationary point charges in a vacuum is proportional to the product of the charges and inversely proportional to the square of the distance between them. The forces on the two charges are equal in magnitude and opposite in direction; if a charge is zero, the electrostatic force between them is zero.
This is a static model: forces and the graph update as soon as you change a parameter.
Electrostatic force vs. separation
Positive values mean repulsion, negative values attraction; the vertical axis rescales automatically.
Think about it
Keeping the charges unchanged, if the distance is increased to 2 times its original value, how does the electrostatic force change?
It decreases to 1/4 of its original value, because F is inversely proportional to r². Changing the sign of either charge switches between attraction and repulsion but does not change the magnitude of the force.
Model assumptionsPoint charges in vacuum · k ≈ 9.0×10⁹ N·m²/C² · Charges held in place by external forces · Arrows show force direction only
Data log
Set the parameters and click “Record data”. Record several rows with different parameters to plot their relationship and fit a straight line; pause and record at different times to study how a reading changes with time.