A rectangular loop ABCD made of uniform wire is a part of an electric circuit shown in the given figure. The length AD = BC = 5 mm. The sides AB and DC are long compared to the other two sides. What will be the magnetic force per unit length acting on the wire AB if the ammeter reading is 8 A?

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.