\(P, Q\) and \(R\) are long parallel straight wire in air, carrying currents \(20 A, 40 A\) and 60 A as shown in figure. What is the direction of the resultant force on Q ?

A Perpendicular to this page
B To the right
C To the left
D Opposite to that of the current in Q.

Verified Solution

Answer & Solution

Correct Answer

(B) To the right

Step-by-step Solution

Detailed explanation

B
Two parallel currents attract each other, and two anti parallel currents will repel each other.
So the force between P and Q will be repulsion and force between Q and \(R\) will be attraction.
So the net force is towards right of wire Q .

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.

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