The sum of two point charges is 7 μC. They repel each other with a force of 1 N when kept 30 cm apart in free space. Calculate the value of each charge.

2μC and 5μC 2μC and 15μC 7μC and 5μC 7μC and 15μC

2μC and 5μC

F = kq1q2/r2 F = 1 N ; k = 9 x 109 N m2/C2 ; r = 30 x 10-2 m q1q2 = 10-11 C2 ∴ charges are : 2μC and 5μC