Coulomb's Law

Electrostatic forces are the attractive and repulsive forces between charged particles. The French engineer and physicist, Charles Coulomb, developed a mathematical formula to derive the magnitude of these forces based on the size of the two charges and the distance between them. These electrostatic forces are often referred to as coulombic forces. These are the forces responsible for holding electrons and nuclei together in atoms, and for creating ionic bonds between two oppositely charged particles or ions. The strength of the coulombic forces directly influences the properties of compounds formed from ions.

This program simulates the effects of ion charge and separation on coulombic forces. Two ions are represented by spheres and the forces of attraction and repulsion are demonstrated by arrows drawn from the spheres. One of the ions (the blue one) can be dragged around using the mouse in order to vary the distance between the two ions. In addition, the sign and magnitude for each ion can be adjusted. (Try dragging the blue ion over the red one!).

The distance between the two ions is reported in Angstroms at the bottom of the screen. The 'Scale' in the screen gives an idea of the distance on the screen. (Try dragging the 'scale',it moves). For comparison,

One Angstrom = 10 pm = 0.01 nm

The relative strength and direction of the forces between the ions is represented by "vector-like" arrows emanating from each ion. The length of the arrow (measured from the center of the ions) is directly proportional to the magnitude of the force (ie, proportional to the product of the charges and inversely proportional to the square of the distance between them). The resultant force is also given at the bottom of the screen in units of Newtons (N).

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INSTRUCTIONS

  1. Adjust the charge of the draggable blue colored ion by clicking on the up or down arrows. The charge can be set between -3 and +3.
  2. Adjust the charge of the non-draggable red colored ion by clicking on the up or down arrows, which again sets the charge between -3 and +3.
  3. Alter the distance between the two ions by depressing the mouse button on the blue ion and dragging it to a new location.
  4. Some interesting features - the scale is draggable and can be relocated anywhere ! Also, though you cannot drag the red ion, you can "push" it around with the blue one.
Last modified: April 13, 2000