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JEE Main 2008 (AIEEE) · Magnetic Field of Straight Wires

Magnetic Field of Straight Wires question from JEE Main 2008 (AIEEE)

Q68JEE Main 2008 · AIEEEMedium

Magnetic Field of Straight Wires

A horizontal overhead powerline is at height of 4 m4\text{ m} from the ground and carries a current of 100 A100\text{ A} from east to west. The magnetic field directly below it on the ground is

(μ0=4π×10−7 T m A−1)\left(\mu_0 = 4\pi \times 10^{-7}\text{ T m A}^{-1}\right)

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Answer: (c)

  1. B=μ0I2πr=2×10−7×1004=5×10−6 TB = \frac{\mu_0 I}{2\pi r} = \frac{2 \times 10^{-7} \times 100}{4} = 5 \times 10^{-6}\text{ T}
  2. Right-hand rule: thumb westward, the field below the wire points south.
  3. So the answer is (c) 5×10−6 T5 \times 10^{-6}\text{ T} southward.
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