TABLE 2.1 : MEASUREMENT OF ELECTRIC CHARGES KINDS OF CHARGES MASS CHARGE Neutron 1.675 X 10-27 kg Proton (+e) 1.673 X 10 7 Kg 1.6 X 10-19 C Electron (e) 9.11 X 10-31 kg 1.6 X 10-15 C COULOMB'S LAW The magnitude of the electric force between two-point charges is directly proportional to product of the charges and inversely proportional to the square of the distances between them. The coulomb's law is defined by the equation: = - | 9: 92 | _ k| q. 92 | ARE. Where: F - Force - Newton (N) q: & q2 - Charge - Coulomb (C) E. - Vacuum ermittivity or permittivity of free space - 8.854x10-12 C3/N.ma k - Proportionality Constant = 9x10" Nim/ / C? = 1 dynes.com//statCa CONVERS 1C = 3x109 statC A point charge (q1) has a magnitude of 7.9x10-6 C. A second charge (q2) has a magnitude of 8.8x10-6 C and is located 2 m from the first charge. Determine the electrostatic force each charge exerts on the other. A 25 C and 75 C charge give off a force of 2.5 x 10+8 N. What is the distance between them? In Figure 2.4, Q, =+20nC and Q2=-20nC, Calculate the potentials at point A, B and C. 14cm 21cm C az B 8cm 8cm 6cm FIG. 2.4