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An infinite wire placed along z-axis, has current \( \mathrm{I}_{1} \) in positive z-direction. A conducting rod placed in xy plane parallel to y- axis has current \( \mathrm{I}_{2} \) in positive y-direction. The ends of the rod subtend angles of \( +30^{\circ} \) and \( -60^{\circ} \) at the origin with positive \( \mathrm{x}- \) direction. The rod is at a distance 'a' from the origin. Find net force on the rod.
PhysicsMagnetic Effects of CurrentJEE Main
Options:
  • A \( \mathrm{F}=\frac{\mu_{0}}{4 \pi} \mathrm{I}_{1} \mathrm{I}_{2} \ell \ln 3(-\widehat{\mathrm{k}}) \)
  • B \( \mathrm{F}=\frac{\mu_{0}}{4 \pi} 2 \mathrm{I}_{1} \mathrm{I}_{2} \ell \mathrm{n} 3(-\widehat{\mathrm{k}}) \)
  • C \( \mathrm{F}=\frac{\mu_{0}}{4 \pi} \mathrm{I}_{1} \mathrm{I}_{2} \ell \mathrm{n} 3(\widehat{\mathrm{k}}) \)
  • D \( \mathrm{F}=\frac{\mu_{0}}{4 \pi} 2 \mathrm{I}_{1} \mathrm{I}_{2} \ell \mathrm{n} 3(\widehat{\mathrm{k}}) \)
Solution:
1130 Upvotes Verified Answer
The correct answer is: \( \mathrm{F}=\frac{\mu_{0}}{4 \pi} \mathrm{I}_{1} \mathrm{I}_{2} \ell \ln 3(-\widehat{\mathrm{k}}) \)


x a = tan θ
x = a tan θ 1
d x = a sec 2 θ d θ
B = μ 0 4 π 2 I 1 r · · · 2
dF = I 2 dx B sin θ - k ^ · · · 3
From (1), (2) & (3)
dF=I2asec2θdθμ04π2I1asecθsinθ (k^)

=μ04π2I1I2sinθsecθdθ(k^)

F=μ02πI1I2-60°30°sinθsecθdθ (k^)

F=μ02πI1I2lncosθ30°-60° (k^)
F=μ04πI1I2n3-k^

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