Two concentric circular coils of 10 turns each are situated in the same plane. Their radii are 20 cm and 40 cm and they carry respectively 0.2 A and 0.3 A current in opposite direction. The magnetic field at the centre is ( μ₀ = 4π × 10⁻⁷ SI units) (a) 4π × 10⁻⁷ T (b) 5π × 10⁻⁷ T (c) 2π × 10⁻⁵ T (d) 7π × 10⁻⁶ T

Answer: (b). Opposite currents: B = (μ₀ N)/(2)((I₁)/(r₁)-(I₂)/(r₂)) B = 4π×10⁻⁷×102((0.2)/(0.2)-(0.3)/(0.4)) = 2π×10⁻⁶×0.25 B = 5π×10⁻⁷ T So the answer is (b).

Two concentric circular coils of 10 turns each are situated in the… | MHT CET 2023 (12 May, Shift 2)

Q63MHT CET 2023 · 12 MAY · SHIFT 2Medium

Biot-Savart Law & Circular Coils

Two concentric circular coils of 10 turns each are situated in the same plane. Their radii are $20\text{ cm}$ and $40\text{ cm}$ and they carry respectively $0.2\text{ A}$ and $0.3\text{ A}$ current in opposite direction. The magnetic field at the centre is ( $\mu_0 = 4\pi \times 10^{-7}$ SI units)

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Answer: (b)

Opposite currents: $B = \dfrac{\mu_0 N}{2}\left(\dfrac{I_1}{r_1}-\dfrac{I_2}{r_2}\right)$
$B = \dfrac{4\pi\times10^{-7}\times10}{2}\left(\dfrac{0.2}{0.2}-\dfrac{0.3}{0.4}\right) = 2\pi\times10^{-6}\times0.25$
$B = 5\pi\times10^{-7}$ T
So the answer is (b).

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Biot-Savart Law & Circular Coils question from MHT CET 2023 (12 May, Shift 2)

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