A horizontal telegraph wire of length 30 m spread east to west fell down freely from a height of 20 m. If the resistance of the wire is \(40 \Omega\) and the horizontal component of the earth's magnetic field at the place is \(2 \times 10^{-5} \mathrm{~T}\), then the induced current when the wire reaches the ground is (Acceleration due to gravity \(=10 \mathrm{~m} \mathrm{~s}^{-2}\) )

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.