Answer: -0.18 J.
- A +0.18 J
- B -0.09 J
- C -0.18 J
- D +0.36 J
Correct answer: C. -0.18 J
Explanation: Potential energy is U = kq<sub>1</sub>q<sub>2</sub>/r = 9 × 10<sup>9</sup> × 2 × 10<sup>-6</sup> × -3 × 10<sup>-6</sup>/0.3 = -0.18 J.
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.