GCSE Combined Science (AQA)

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Magnetic Field Strength

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Magnetism and electromagnetism Permanent and induced magnetism, magnetic forces and fields

Magnetic Field Strength

3:16 Introduction to Magnetic Fields
Spec 4.7.1.2
Previous Magnetic Field Lines Next Magnetic Field Around the Earth
  • Magnetic objects experience a force in the magnetic field around a magnet.
  • A bar magnet and a steel screw are examples of a magnet and a magnetic object.
  • The screw becomes an induced magnet with a north pole facing the bar magnet's south pole.
  • Unlike poles cause the screw to experience an attractive force towards the magnet.
  • The strength of the magnetic field affects the force experienced by a magnetic object.
  • The magnetic field strength decreases with distance from the magnet.
  • A screw far from the magnet experiences a weak force and moves slowly towards it.
  • A screw close to the magnet experiences a strong force and moves quickly towards it.
  • Field strength is maximum at the poles where field lines are closest.
  • Magnetic field lines indicate the direction of force on a north pole in the field.
  • A compass can trace out field lines for a bar magnet.
  • Field lines start at the north pole and finish at the south pole.
  • Closer field lines indicate stronger magnetic forces.
  • Field lines are denser near the poles, indicating a strong field.
  • Field lines are sparse away from the poles, indicating a weak field.
  • For exams, be able to draw field line patterns for a bar magnet and explain field strength variations.

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