Path of a Charged Particle in a Magnetic Field

Path of a Charged Particle in a Magnetic Field MDCAT MCQs with answers

6 past paper MCQs on Path of a Charged Particle in a Magnetic Field, from the Electromagnetism unit of MDCAT Physics. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

Read the notes first Practise the unit as a quiz

1.The path of a charged particle in a plane perpendicular to a uniform magnetic field is: (NUMS MDCAT 2025)

  1. Circular
  2. Helical
  3. Parabola
  4. Elliptical
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Correct answer: (a) Circular

With the velocity always at right angles to the field, the magnetic force is centripetal and the path is a circle.

2.If mass of a charged particle is doubled, cyclotron frequency becomes: (NUMS MDCAT 2025)

  1. Doubled
  2. Halved
  3. Quadrupled
  4. One fourth
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Correct answer: (b) Halved

The cyclotron frequency is $qB/2\pi m$, so twice the mass halves it.

3.When a charged particle enters the magnetic field parallel then it will: (SZABMU MDCAT 2023)

  1. Deflect toward north
  2. Deflect toward south
  3. Move straight
  4. Move in circular path
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Correct answer: (c) Move straight

With the velocity along the field the sine is zero, so there is no force and the path stays straight.

4.When a charged particle enters the magnetic field parallel, it will: (NUMS MDCAT 2023)

  1. Deflect toward north
  2. Deflect toward south
  3. Move straight
  4. Move in circular path
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Correct answer: (c) Move straight

With the velocity along the field there is no force, so the path is a straight line.

5.A charged particle moving with velocity v, enters a uniform magnetic field B. The direction of v is perpendicular to B. What is the path of the charged particle inside the magnetic field? (PMC Practice 2021)

  1. Parabolic
  2. Circular
  3. Parallel to v
  4. Parallel to B
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Correct answer: (b) Circular

The force is always at right angles to the velocity, so the path curls into a circle.

6.A proton is projected with a uniform velocity ‘v’ along the axis of a current carrying solenoid. (UHS MDCAT 2017)

  1. The proton will be accelerated along the axis.
  2. The proton path will be circular about the axis.
  3. The proton moves along a helical path.
  4. The proton will continue to move with velocity ‘v’ along the axis.
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Correct answer: (d) The proton will continue to move with velocity ‘v’ along the axis.

The velocity lies along the field inside the solenoid, so there is no magnetic force at all.

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