Question

two point charges each have values of +300 and - 3000C and are seperated by a distance of 4.00cm. what is electric field midway between the two charges?

Answer 1

E.F due to +ve charge will be away from charge, E.F due to -ve charge will be towards the charge.

E1 = Electric field at point P ( mid point ) due to charge q1

E1 = K*q1/ r²

    = 9*10⁹ *300/ (2*10^-2)²                           ( k = 1/4*pie*E₀ = 9*10⁹ )

   = 6.75*10¹⁵ N/C

E2 = electric field at P due to charge q2

E2 = k*q2 / r²

    = 9*10⁹*3000 / (2*10^-2)²

   = 6.75*10¹⁶ N/C

from fig, E1 and E2 are in same direction:

net electric field, E = E1 +E2 = 7.425*10¹⁶ N/C                  ( towards -ve charge)