# Electric force - Electrostatics

### Electric force

#### Lessons

###### In this lesson, we will learn: Coulomb's law, which gives the electric force that one charged object exerts on another Calculating electric force for different arrangements of chargesNotes: Electrostatics deals with electric charges that are at rest ("static") Charge is a scalar quantity. It can be positive or negative. The positive or negative character of a charge is called polarity. Like gravity, electric forces act at a distance. Unlike gravity, which always pulls objects together, electric forces can either push apart or pull together charges. Like charges (both positive or both negative) will repel each other Opposite charges (one positive and one negative) will attract each other. Coulomb's law describes electric force (Fe). $|F_e| = k \frac{|Q_1 Q_2|}{r^2}$ k (Coulomb's constant) is an experimentally determined constant that relates the size of the charges (Q1 and Q2) and radius (r¸ distance between charges) to the magnitude Fe. Coulomb's law only gives the magnitude of Fe and not the direction, indicated by the absolute value sign on |Fe|. Notice that k, Q, and $r^2$ are all scalars: there are no vectors on that side of the equation that could give Fe a direction. The direction of Fe must be found by considering if the charges involved would be attracted or repelled, based on their polarities. Coulomb's Law (Electric Force) $|F_e| = k \frac{|Q_1 Q_2|}{r^2}$$|F_e|:$ magnitude of electric force, in newtons (N)$k:$ Coulomb's law constant, $9.00 \times 10^9 N\centerdot m^2 / C^2$$|Q_1|, |Q_2|:$ magnitude of each charge, in coulombs (C)$r:$ distance between charges, in meters (m) 