2)
e0 is called the permittivity of free space The value
of e0 in SI units is
0
 = 8 854 × 10–12 C2 N–1m–2
Since force is a vector, it is better to write
Coulomb’s law in the vector notation Let the position
vectors of charges q1 and q2 be r1 and r2 respectively
[see Fig