Question

Three infinitely long parallel straight current-carrying wires A, B and C are kept at equal distance from each other as shown in the figure. The wire C experiences net force F. The net force on wire C, when the current in wire A is reversed will be ______.

पर्याय

• Zero

• F/2

• F

• 2F

Answer 1

Three infinitely long parallel straight current-carrying wires A, B and C are kept at equal distance from each other as shown in the figure. The wire C experiences net force F. The net force on wire C, when the current in wire A is reversed will be zero.

Explanation:

Let F₁ is force per unit, length between A & C

∴ i.e. `"F"_1 = mu_0/(4pi)  (2"I" xx "I")/"2r"`

And F₂ is force per unit, length between B & C

∴ `"F"_2 = mu_0/(4pi)  ("I" xx "I")/"r"`

Now net force on ‘C’ is per unit length

`"F"_1 + "F"_2 = mu/(4pi)  "I"^2/"r"  (1 + 1)`

`= (2mu_0)/(4pi)  "I"^2/"r"` = F  (given)

Now following figure.

`"F'"_1` = Repulsive force between A & C

`= mu_0/(4pi)  (2"I"^2)/(2"r")`

`"F'"_2 = "F"_2` = A reactive force between B & C

∴ Net force 'C' `"F'"_2 - "F"_2 = 0`

`because "F'"_1 = "F'"_2 = mu/(4pi)  (2"I"^2)/(2"r")`

∴ Net Force on ‘C’ is zero.