Electric force

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Electric force in one dimension
Three point charges are fixed in positions as shown. Find the net force acting on $Q_1$ $Q_{1}$ .
Electric force in two dimensions
Three point charges are fixed in positions as shown. Find the net force acting on $Q_1$ $Q_{1}$ .

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 charges

Notes:

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.

|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 F_e.
Coulomb's law only gives the magnitude of F_e and not the direction, indicated by the absolute value sign on |F_e|. Notice that k, Q, and $r^2$ are all scalars: there are no vectors on that side of the equation that could give F_e a direction. The direction of F_e 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)