1. A charge −1.0 × 10^−5 C is fixed on the x-axis at 10 m, and a charge 9 × 10^−6 C is fixed on the y-axis at 3 m. Calculate the magnitude of the resultant electric field E at the origin. Answer in units of N/C.

2. Calculate the electric potential at the origin. Answer in units of V.

3. A −3 × 10^−6 C charge is brought from a very distant point by an external force and placed at the origin. Calculate the magnitude of the electric force on this charge. Answer in units of N.

4. Calculate the work that had to be done by an external force to bring Q to the origin from the distant point. Answer in units of J.