A conducting spherical shell is earthed. A positive charge \( +q_{1} \) is placed at the center ...

A conducting spherical shell is earthed. A positive charge \( +q_{1} \) is placed at the center and another small positive charge \( +q_{2} \) is placed at a distance \( r \) from \( q_{1} \) (see figure). Ignore the effect of induced charge due to \( q_{2} \) on the sphere. Then the coulomb force on \( q_{2} \) is
(1) zero
(2) \( \frac{q_{1} q_{2}}{4 \pi \varepsilon_{0} r^{2}} \)
(3) \( \frac{q_{1} q_{2}}{4 \pi \varepsilon_{0}(r-R)^{2}} \)
(4) \( \frac{q_{1} q_{2}}{4 \pi \varepsilon_{0}\left(r^{2}-R^{2}\right)} \)