In SI units, the unit of charge is coulomb The experimental value of
the constant e0 is
e0 = 8 854 × 10–12 C2 N–1 m–2
The approximate value of k is
k = 9 × 109 N m2 C–2
6 The ratio of electric force and gravitational force between a proton
and an electron is
2
39
2 4
10
e
p
k e