Answer: kQr/R 3.
- A kQ/r<sup>2</sup> (same as outside)
- B kQr/R<sup>3</sup>
- C Zero
- D kQ/R<sup>2</sup> x r
Correct answer: B. kQr/R<sup>3</sup>
Explanation: Inside solid sphere: only the charge within radius r contributes. Q<sub>enclosed</sub> = Q(r/R)<sup>3.</sup> E = kQ_enclosed/r<sup>2</sup> = kQr/R<sup>3.</sup>
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.