What is the formula for electric force?



F=k*qa*qb/(r^2) Here, F is the force between the particles, qa and qb are the charges of particles a and b. The separation between the particles is r, and k is a constant, 8.99x109 (Nm2/C2). Note that the force falls off quadratically, similarly to the behavior of the gravitational force. The force is attractive, when F is negative, hence when the charges have opposite sign. Opposites attract - like charges repel. Of course, remember that force is a vector, which in this case points parallel to r.


E = F / q where E (electric field) and F (electric field force) are vectors and q is the charge. The electric field vector is directed radially outward from a positive charge and radially in toward a negative point charge. Positive repels positive.


Electric field E= k Q/r^2. The force on charge e by a charge Q is keQ/r^2 k is a constant which nearly 10^9.