q. Two point charges of +16 micro coulomb and -9 micro coulomb are placed 8 cm apart in air .Determine the position of the point at which the resultant field is zero .

Consider an axial point x cm away from -9 micro C.Then Electric field intensity at that point will be

(k X (16 micro) / (8+x)² )+(k X (-9 micro) / (x)² )

But given it is zero so

we have 16/(8+x)² = 9 / x²

or x / x+ 8 = 3 / 4

or x =24 cm

so Electric field is zero at 24 cm on the axial line from -9 micro C charge