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NEET 2026
Exam
NEET
Year
2026
Subject
Physics
Chapter
Chapter

NEET 2026 · Physics · Chapter

A conducting wire is bent into a circular arc of radius 2 cm and...

A conducting wire is bent into a circular arc of radius 2 cm2\text{ cm} and subtends an angle of 60∘60^\circ at its centre. If a steady current of 12 A12\text{ A} is passed through the wire, what is the magnitude of the magnetic field produced at the centre of the arc?
(Take the permeability of free space μ0=4π×10−7 T m A−1\mu_0 = 4\pi \times 10^{-7}\text{ T m A}^{-1})

Options

  1. A10π μT10\pi\text{ }\mu\text{T}
  2. B20π μT20\pi\text{ }\mu\text{T}
  3. C120π μT120\pi\text{ }\mu\text{T}
  4. D40π μT40\pi\text{ }\mu\text{T}

Correct answer

B. 20π μT20\pi\text{ }\mu\text{T}

Step-by-step solution

The magnetic field at the centre of a circular arc is given by the formula:

B=μ0I4πRθB = \dfrac{\mu_0 I}{4\pi R} \theta

Given:
I=12 AI = 12\text{ A}
R=2 cm=2×10−2 mR = 2\text{ cm} = 2 \times 10^{-2}\text{ m}
θ=60∘=π3 rad\theta = 60^\circ = \dfrac{\pi}{3}\text{ rad}
μ0=4π×10−7 T m A−1\mu_0 = 4\pi \times 10^{-7}\text{ T m A}^{-1}

Substituting the values into the formula:

B=4π×10−7×124π×2×10−2×π3B = \dfrac{4\pi \times 10^{-7} \times 12}{4\pi \times 2 \times 10^{-2}} \times \dfrac{\pi}{3}

B=10−7×122×10−2×π3B = \dfrac{10^{-7} \times 12}{2 \times 10^{-2}} \times \dfrac{\pi}{3}

B=6×10−5×π3B = 6 \times 10^{-5} \times \dfrac{\pi}{3}

B=2π×10−5 TB = 2\pi \times 10^{-5}\text{ T}

B=20π×10−6 T=20π μTB = 20\pi \times 10^{-6}\text{ T} = 20\pi\text{ }\mu\text{T}

Answer: 20π μT20\pi\text{ }\mu\text{T}
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