The adjacent figure shows the cross-section of a long rod with its length perpendicular to the plane of the paper. It carries a constant current flowing along its length. B1, B2, B3 and B4 respectively represent the magnetic fields due to the current in the rod at points 1,2,3 and 4 lying at different separations from the center O, as shown in the figure. Which of the following shall hold true?

Question

The adjacent figure shows the cross-section of a long rod with its length perpendicular to the plane of the paper. It carries a constant current flowing along its length. B1, B2, B3 and B4 respectively represent the magnetic fields due to the current in the rod at points 1,2,3 and 4 lying at different separations from the center O, as shown in the figure. Which of the following shall hold true? (A) B1>B2 ≠ 0 (B) B2>B3 ≠ 0 (C) B1>B2=B3=0  (D) B3>B4 ≠ 0

Tardigrade Admin · Accepted Answer

Magnetic field outside the long rod ∵ B=(μ0 i/2 π r) ∴ B3>B4 ≠ 0

$B_{1} > B_{2} \neq = 0$

$B_{2} > B_{3} \neq = 0$

$B_{1} > B_{2} = B_{3} = 0$

$B_{3} > B_{4} \neq = 0$

Magnetic field outside the long rod
$∵ B = \frac{μ _{0} i}{2 π r}$
$∴ B_{3} > B_{4} \neq = 0$

B1​>B2​=0

B2​>B3​=0

B1​>B2​=B3​=0

B3​>B4​=0

Magnetic field outside the long rod ∵B=2πrμ0​i​ ∴B3​>B4​=0

$B_{1} > B_{2} \neq = 0$

$B_{2} > B_{3} \neq = 0$

$B_{1} > B_{2} = B_{3} = 0$

$B_{3} > B_{4} \neq = 0$

Magnetic field outside the long rod
$∵ B = \frac{μ _{0} i}{2 π r}$
$∴ B_{3} > B_{4} \neq = 0$