# Electric force

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###### Topic Notes

In this lesson, we will learn:

$|F_e|:$ 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)

- 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.
- 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 (*F*)._{e}-
*k*(Coulomb's constant) is an experimentally determined constant that relates the size of the charges (*Q*and_{1}*Q*) and radius (_{2}*r*¸ distance between charges) to the magnitude*F*._{e} - Coulomb's law only gives the magnitude of
*F*and not the direction, indicated by the absolute value sign on |_{e}*F*|. Notice that_{e}*k*,*Q*, and $r^2$ are all scalars: there are no vectors on that side of the equation that could give*F*a direction. The direction of_{e}*F*must be found by considering if the charges involved would be attracted or repelled, based on their polarities._{e}

**Coulomb's Law (Electric Force) **

$|F_e|:$ 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)

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