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NEET 2014 (AIPMT) · Magnetic Field of Straight Wires

Magnetic Field of Straight Wires question from NEET 2014 (AIPMT)

Q65NEET 2014 · AIPMTMedium

Magnetic Field of Straight Wires

Two identical long conducting wires AOBAOB and CODCOD are placed at right angle to each other, with one above other such that OO is their common point for the two. The wires carry II1 and II2 currents, respectively. Point PP is lying at distance f from OO along a direction perpendicular to the plane containing the wires. The magnetic field at the point PP will be

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Answer: (d)

  1. P is at perpendicular distance dd from both long wires (P lies above their crossing point O).
  2. B1=μ0I12πdB_1 = \frac{\mu_0 I_1}{2\pi d}, B2=μ0I22πdB_2 = \frac{\mu_0 I_2}{2\pi d}; since the wires are perpendicular, B1⊥B2B_1 \perp B_2.
  3. B=B12+B22=μ02πd(I12+I22)1/2B = \sqrt{B_1^2 + B_2^2} = \frac{\mu_0}{2\pi d}\left(I_1^2 + I_2^2\right)^{1/2}
  4. So the answer is (d).
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