A, B and C are three parallel conductors of equal lengths carrying currents I, I and 2I respectively. Distance between A and B is ' x ' and that between B and C is also ' x '. F₁ is the force exerted by conductor B on A. F₂ is the force exerted by conductor C on A. Current I in A and I in B are in same direction and current 2I in C is in opposite direction. Then (a) F₁ = F₂ (b) F₂ = 2F₁ (c) F₁ = 2F₂ (d) F₁ = -F₂

Answer: (d). F₁ (B on A): same direction currents, attraction towards B; magnitude (μ₀ I²)/(2π x) per unit length. F₂ (C on A): opposite currents, repulsion away from C; magnitude (μ₀ I·2I)/(2π(2x)) = (μ₀ I²)/(2π x). Equal magnitudes, opposite directions: F₁ = -F₂ So the answer is (d).

A, B and C are three parallel conductors of equal lengths carrying… | MHT CET 2021 (21 Sep, Shift 2)

Q45MHT CET 2021 · 21 SEP · SHIFT 2Medium

Force on Current-Carrying Conductors

A, B and C are three parallel conductors of equal lengths carrying currents $I, I$ and $2I$ respectively. Distance between A and B is ' $x$ ' and that between B and C is also ' $x$ '. $F_1$ is the force exerted by conductor $B$ on $A.\ F_2$ is the force exerted by conductor $C$ on $A$ . Current $I$ in $A$ and $I$ in $B$ are in same direction and current $2I$ in $C$ is in opposite direction. Then

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Answer: (d)

$F_1$ (B on A): same direction currents, attraction towards B; magnitude $\frac{\mu_0 I^2}{2\pi x}$ per unit length.
$F_2$ (C on A): opposite currents, repulsion away from C; magnitude $\frac{\mu_0 I\cdot2I}{2\pi(2x)} = \frac{\mu_0 I^2}{2\pi x}$ .
Equal magnitudes, opposite directions: $F_1 = -F_2$
So the answer is (d).

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Force on Current-Carrying Conductors question from MHT CET 2021 (21 Sep, Shift 2)

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