Answer: 4 x 10 9 N attractive.
- A 4 x 10<sup>9</sup> N attractive
- B 4 x 10<sup>9</sup> N repulsive
- C 1.33 x 10<sup>10</sup> N attractive
- D 1.33 x 10<sup>10</sup> N repulsive
Correct answer: A. 4 x 10<sup>9</sup> N attractive
Explanation: F = kq<sub>1</sub>q<sub>2</sub>/r<sup>2</sup> = 9 x 10<sup>9</sup> x 4 x 1 / 9 = 4 x 10<sup>9</sup> N. Negative product means attractive.
Field lines always point from positive to negative charge, are denser where the field is stronger, and never cross; an isolated positive charge has lines radiating symmetrically outward, while a dipole's lines curve from the positive to the negative charge.
Concept context
Coulomb's law, electric field, potential, capacitors, Gauss's law.