Question

Two parallel conductors a and b separated by distance \(d\) carry the same current. If the distance is doubled, the ratio of forces on conductor b before and after separation is:

• A. 2:1
• B. 6:2
• C. 1:4
• D. 4:6

Hint:

Force between parallel current-carrying wires varies inversely with separation distance.

Answer 1

The Correct Option is A

Step 1: Force per unit length between parallel currents.
F ∝ 1/d.

Step 2: Initial force.
F₁ ∝ 1/d.

Step 3: Force after doubling separation.
F₂ ∝ 1/(2d).

Step 4: Forming the ratio.
F₁ : F₂ = (1/d) : (1/2d).

Step 5: Simplifying.
F₁ : F₂ = 2 : 1.

Step 6: Conclusion.
The ratio is 2:1.