Coulom

b’s Law

• Charles Coulomb (1736-1806: French)–Studied relationship between

force and charge Unit of charge = 1 coulomb (C)

The charge on 1 electron is (1.6 x 10-19 C)

Coulom

b’s Law

• The LAW!– Force directly related to magnitude of

the charges– Force inversely related to the square of

the distance between the two charges

F = r2kqQ

F α q Q

r2

1F α

r2q QF α

k is a constant that corrects the proportion into an equality.

F = r2k qQ

• This is similar to a formula • we talked about in Lesson 5.

Only Attractiv

e

Attractive or

Repulsive

F = r2

G mM

Newton’sLawOf

Universal Gravitation

Coulomb’sLaw

Coulom

b’s Law

Product of

masses

Product of

charges

F = r2

G mM

F = r2k qQ

• Keep comparing:

Coulom

b’s Law

• Keep Comparing:

Both areinverse-squarelawsF = r2

G mM

F = r2k qQ

• Keep Comparing

F = r2

G mM

9 x 109 N·m2/C2

Large Magnitude

6.67 x 10-11 N·m2/kg2

Small Magnitude

F = r2k qQ

Electric Fields: An area around a charged object that affects all other charged objectsUnit: N/C

The more the lines the stronger the field

Two More Rules for Drawing Electric Field Lines:

Lines are always drawn out of the positive and into the negative.

The more the lines the stronger the field.