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NEET 2021 · Moving Charge in a Magnetic Field

Moving Charge in a Magnetic Field question from NEET 2021

Q67NEET 2021Medium

Moving Charge in a Magnetic Field

An infinitely long straight conductor carries a current of 5A as shown. An electron is moving with a speed of 105 m/s parallel to the conductor. The perpendicular distance between the electron and the conductor is 20cm at an instant. Calculate the magnitude of the force experienced by the electron at that instant.

Figure

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Answer: (a)

  1. Field of the wire: B=μ0I2πr=2×10−7×50.2=5×10−6 TB = \dfrac{\mu_0 I}{2\pi r} = \dfrac{2\times10^{-7}\times5}{0.2} = 5\times10^{-6}\text{ T}
  2. v⃗\vec v is parallel to the wire, so v⃗⊥B⃗\vec v \perp \vec B: F=evBF = evB
  3. F=1.6×10−19×105×5×10−6=8×10−20 NF = 1.6\times10^{-19}\times10^{5}\times5\times10^{-6} = 8\times10^{-20}\text{ N}
  4. So the answer is (a) 8×10−20 N8\times10^{-20}\text{ N}.
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