Q

- q

rF

F

Distance r 36Force f 36

18144

9576

Charged pith balls

Torsion wire (eg μN

per degree of twist)

Counter weight

+

-

Q

- q

rF

F

Distance r 36Force f 36

18144

9576

Torsion wire (eg μN

per degree of twist)

Charged pith balls

Charged pith balls

Torsion wire (eg μN

per degree of twist)

Counter weight

+

-

Charles Coulombs apparatus 1784

Q

- q

rF

F

Distance r 36Force f 36

18144

9576

Torsion wire (eg μN

per degree of twist)

Charged pith balls

Charles Coulombs apparatus 1784

The force between two charges is proportional to each of the chargesand inversely proportional to the square of their distance apart.

Q

- q

rF

F

The force between two charges is proportional to each of the chargesand inversely proportional to the square of their distance apart.

The electrostatic force can be either positive or negative. + + , _ _ repell, + _ attract

Q

- q

rF

F

The force between two charges is proportional to each of the chargesand inversely proportional to the square of their distance apart.

The electrostatic force can be either positive or negative. + + , _ _ repell, + _ attract

Q

- q

rF

F

F = k qQ r2

k = 9.0x 109

(N m2 C- 2 )

The force between two charges is proportional to each of the chargesand inversely proportional to the square of their distance apart.

The electrostatic force can be either positive or negative. + + , _ _ repell, + _ attract

Q

- q

rF

F

F = k qQ r2

k = 9.0x 109

(N m2 C- 2 )

The force between two charges is proportional to each of the chargesand inversely proportional to the square of their distance apart.

The electrostatic force can be either positive or negative. + + , _ _ repell, + _ attract

Q

- q

rF

F

F = k qQ r2

k = 9.0x 109

(N m2 C- 2 )

The value of k is large so the forces between charges are measurable. Its value depends on the material between the charges. k = 1 4 0

The force between two charges is proportional to each of the chargesand inversely proportional to the square of their distance apart.

The electrostatic force can be either positive or negative. + + , _ _ repell, + _ attract

Q

- q

rF

F

F = k qQ r2

k = 9.0x 109

(N m2 C- 2 )

The value of k is large so the forces between charges are measurable. Its value depends on the material between the charges. k = 1 4 0

0 = 8.85x 10-12 Fm- 1