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JEE Main 2019 (9 Apr, Shift 1) · Force on Current-Carrying Conductors

Force on Current-Carrying Conductors question from JEE Main 2019 (9 Apr, Shift 1)

Q48JEE Main 2019 · 9 APR · SHIFT 1Medium

Force on Current-Carrying Conductors

A rigid square loop of side 'a' and carrying current I2 is lying on a horizontal surface near a long current I1 carrying wire in the same plane as shown in figure. The net force on the loop due to wire will be:

Figure

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Answer: (a)

  1. Forces on the top and bottom sides cancel.
  2. Near side (distance aa) carries current opposite to I1I_1: repulsion μ0I1I2a2πa=μ0I1I22π\frac{\mu_0 I_1 I_2 a}{2\pi a} = \frac{\mu_0 I_1 I_2}{2\pi}.
  3. Far side (distance 2a2a) carries current along I1I_1: attraction μ0I1I2a2π(2a)=μ0I1I24π\frac{\mu_0 I_1 I_2 a}{2\pi (2a)} = \frac{\mu_0 I_1 I_2}{4\pi}.
  4. Net =μ0I1I22π−μ0I1I24π=μ0I1I24π= \frac{\mu_0 I_1 I_2}{2\pi} - \frac{\mu_0 I_1 I_2}{4\pi} = \frac{\mu_0 I_1 I_2}{4\pi}, repulsive.
  5. So the answer is (a).
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