Edexcel iGCSE Physics -6.11P Force on a Charged Particle in a Magnetic Field- Study Notes- New Syllabus

Edexcel iGCSE Physics -6.11P Force on a Charged Particle in a Magnetic Field- Study Notes- New syllabus

Edexcel iGCSE Physics -6.11P Force on a Charged Particle in a Magnetic Field- Study Notes -Edexcel iGCSE Physics – per latest Syllabus.

Key Concepts:

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Edexcel iGCSE Physics -Concise Summary Notes- All Topics

Force on a Moving Charged Particle in a Magnetic Field

When a charged particle moves through a magnetic field, it may experience a force. This force depends on the direction of motion of the particle relative to the magnetic field.

Key Statement

Statement: A charged particle moving in a magnetic field experiences a force provided its motion is not parallel to the magnetic field.

Key idea: The magnetic force only acts on moving charges.

When Does the Force Act?

  • If the particle moves perpendicular to the magnetic field → force is maximum.
  • If the particle moves at an angle to the field → force acts.
  • If the particle moves parallel to the field → no force acts.
  • If the particle is stationary → no force acts.

Important point: The force depends on the component of velocity perpendicular to the magnetic field.

Direction of the Magnetic Force

  • The force is perpendicular to both the direction of motion and the magnetic field.
  • This causes the particle’s path to change direction, not speed.
  • For a positive charge, the direction follows Fleming’s left-hand rule.
  • For a negative charge, the force acts in the opposite direction.

Effect on the Motion of the Particle

  • The force provides centripetal force.
  • The particle may follow a curved or circular path.
  • The speed remains constant, but the direction changes.

Why No Force Acts When Motion Is Parallel

  • Magnetic force depends on motion across field lines.
  • Parallel motion does not cut magnetic field lines.
  • No interaction → no force.

Example

An electron enters a uniform magnetic field with its velocity perpendicular to the field direction. Describe the motion of the electron and explain why this motion occurs.

▶️ Answer / Explanation
  • The electron experiences a magnetic force.
  • The force is perpendicular to its velocity.
  • The force changes the direction but not the speed.
  • The electron follows a curved or circular path.
  • The force provides centripetal acceleration.

Example

A proton moves through a magnetic field parallel to the field lines. Explain why the proton is not deflected.

▶️ Answer / Explanation
  • The proton is moving parallel to the magnetic field.
  • There is no component of velocity perpendicular to the field.
  • Magnetic force depends on cutting field lines.
  • No magnetic force acts on the proton.
  • The proton continues in a straight line.
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