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NEET Physics Magnetic Effects of Current 2025 NEET 2025

NEET Physics Question (2025) — Solution

Question

An electron (mass 9 10^ -31 ~kg and charge 1.6 10^ -19 C ) moving with speed c / 100( c = speed of light) is injected into a magnetic field B of magnitude 9 10^ -4 ~T perpendicular to its direction of motion. We wish to apply an uniform electric field E together with the magnetic field so that the electron does not deflect from its path. Then (speed of light c =3 10^8 ~ms ^ -1 )

Options

  1. A. E is perpendicular to B and its magnitude is 27 10^4 ~V ~m ^ -1
  2. B. E is perpendicular to B and its magnitude is 27 10^2 Vm ^ -1
  3. C. E is parallel to B and its magnitude is 27 10^2 ~V ~m ^ -1
  4. D. E is parallel to B and its magnitude is 27 10^4 ~V ~m ^ -1

Answer

B. E is perpendicular to B and its magnitude is 27 10^2 Vm ^ -1

Step-by-step solution

For particle To Remain undeflected aligned & F _e=- F _ m \\ & | E |= VB \\ & E = c 100 9 10^ -4 90 \\ & E =27 10^2 ~V / m and \\ & E = B V aligned

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