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Moving Charges and Magnetism — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsMoving Charges and Magnetism1 Mark
MCQ
A particle moves in a region having a uniform magnetic field and a parallel, uniform electric field. At some instant, the velocity of the particle is perpendicular to the field direction. The path of the particle will be:
  • A
    A straight line.
  • B
    A circle.
  • C
    A helix with uniform pitch.
  • ✓
    A helix with nonuniform pitch.
✓

Answer

Correct option: D.
A helix with nonuniform pitch.

$\text{F}=\text{q}\vec{\text{E}}+\text{q}(\vec{\text{V}}\times\vec{\text{B}})$
$\text{F}=\text{q}\vec{\text{E}}$ provides the acceleration in $'x'$ direction.
$\text{F}_2=\text{}\text{q}(\vec{\text{V}}\times\vec{\text{B}})$ provides the centripetal Force.
The path of the particle will be ahelix with nonuniform pitch.

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