Physics - Magnetism Question with Solution | TestHub

PhysicsMagnetismBiot-savart's & Ampere's Circuital lawEasy2 minPYQ_2020
PhysicsEasysingle choice

An infinite wire placed along z-axis, has current I 1  in positive z-direction. A conducting rod placed in xy plane parallel to y-axis has current I 2  in positive y-direction. The ends of the rod subtend angles of +30o and -60o at the origin with positive x-direction. The rod is at a distance 'a' from the origin. Find net force on the rod.

Options:

Answer:
A
Solution:



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 → = I 2 asec 2 θ d θ . μ 0 4 π 2 I 1 a sec θ . sin θ = μ 0 4 π 2 I 1 I 2 sin θ sec θ d θ ( − k ^ )

F → = μ o 4π 2 I 1 I 2      ∫  −30 ∘ 60 ∘ tanθdθ= μ o 4π 2 I 1 I 2 [ − log e cosθ ] − 30 ∘ 60 ∘ ( − k ^ ) F → = μ o 4π 2 I 1 I 2 [ − log e cos 60 ∘ + log e cos( − 30 ∘ ) ]= μ o 4π 2 I 1 I 2 [ log e 3 2 ×2 ] ( − k ^ ) F → = μ o 4π  I 1 I 2 ln3( − k ^ )

Subject:PhysicsTopic:MagnetismSubtopic:Biot-savart's & Ampere's Circuital law
⏱ 2mℹ️ Source: PYQ_2020

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