d
(d) \({E_x} = - \frac{{dV}}{{dx}} = - (6 - 8{y^2}),\)\({E_y} = - \frac{{dV}}{{dy}} = - ( - \,16xy - 8 + 6z)\)
\({E_z} = - \frac{{dV}}{{dz}} = - \,(6y - 8z)\)
At origin \(x = y = z = 0\) so,\({E_x} = - \,6,\,{E_y} = 8\) and \({E_z} = 0\)
\(==>\) \(E = \sqrt {E_x^2 + E_y^2} = 10\,N/C\).
Hence force \(F = QE = 2 \times 10 = 20\,N\)