Coulomb's Law for Three Point Charges
Coulomb's Law for Three Point Charges
Coulomb's law states that the force between two charges and separated by a distance is proportional to the signed magnitudes of the charges and inversely proportional to . In SI units, charge is measured in coulombs (C) and distance in meters (m). The constant equals , giving the force in newtons (N):
q
1
q
2
r
2
r
1/4π
ϵ
0
8.9875×
9
10
F=
1
4π
ϵ
0
q
1
q
2
2
r
This Demonstration describes the interaction of three point charges. Charge 1 is fixed in space; you can vary the distances from charge 1 to charge 2 and charge 1 to charge 3, as well as the angle between charges 2 and 3. The two plots at the bottom show the forces and between charges 1 and 2 and between charges 1 and 3 as a function of distance. The top-right plot is the total force on charge 1, which is the sum of the two vectors and (so it depends on the angle between two charges):
F
12
F
13
F
total
F
12
F
13
||=
F
total
+-2||cos(θ)
2
F
12
2
F
13
F
12
F
13