Two charged particles each of mass \(9.8 \mathrm{~g}\) and charges \(+20 \mu \mathrm{C}\) and \(-20 \mu \mathrm{C}\) are attached to the two ends of a massless and rigid uniform non-conducting rod of length \(50 \mathrm{~cm}\). This arrangement is held in a uniform electric field of \(12.1 \mathrm{NC}^{-1}\), such that the rod makes a very small angle with the field direction. If the rod is set free, the minimum time needed for the rod to become parallel to the direction of the electric field is ................ seconds.

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.