Question

two positive point charges which are 0.1metre apart repel each other with a force of 18 Newton. if the sum of the charges be 9 micro coulomb. Calculate their separate value.

Answer 1

The Coulomb's law of force between two electrically charged particles :         q₁ , q₂ = electric charges on the two particles.           r = distance between two particles = 0.1 m      the particles are assumed to be point sized.         Force F = 18 N  
        q₁ + q₂ = 9 μ C    --- (1)


  Solve the two equations to get the values of charges.     q₁ (9 - q₁) = 20     q₁² - 9 q₁ + 20 = 0       (q₁ - 5) (q₁ - 4) = 0
       q₁ = 5 μ C  or  4 μ C       q₂  = 4 μ C  or  5 μ C