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Question: Answered & Verified by Expert
A current \(I\) a flows in a circular arc of radius \(r\) subtending an angle \(\theta\) as shown in the figure. Find the magnetic field at the centre \(O\) of the circle.

PhysicsMagnetic Effects of CurrentAP EAMCETAP EAMCET 2020 (17 Sep Shift 1)
Options:
  • A \(\frac{\mu_0 I \theta}{4 \pi r}\)
  • B \(\frac{2 \mu_0 I \cdot \sin \theta}{4 \pi r}\)
  • C \(\frac{2 \mu_0 I \sin \theta}{2 r}\)
  • D \(\frac{2 \mu_0 I \sin \theta}{4 r}\)
Solution:
2397 Upvotes Verified Answer
The correct answer is: \(\frac{\mu_0 I \theta}{4 \pi r}\)
Magnetic field at the centre due to current carrying circular loop is given as
\(B_C=\frac{\mu_0 I}{2 r}\) ...(i)


Magnetic field due to current carrying circular arc making an angle \(\theta\) at the centre, is given as
\(\begin{aligned}
& B=\frac{\theta}{2 \pi} \cdot B_C=\frac{\theta}{2 \pi} \cdot \frac{\mu_0 I}{2 r} \text { [From Eq. (i)] } \\
& B=\frac{\mu_0 I \theta}{4 \pi r}
\end{aligned}\)

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