Answer: 4 x 109 N attractive.
- A 4 x 109 N attractive
- B 4 x 109 N repulsive
- C 1.33 x 1010 N attractive
- D 1.33 x 1010 N repulsive
Correct answer: A. 4 x 109 N attractive
Explanation: F = kq1q2/r2 = 9 x 109 x 4 x 1 / 9 = 4 x 109 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.