Fleming's Left Hand Rule (Edexcel GCSE Physics)

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Fleming's Left Hand Rule

Higher Tier Only

  • The direction of the force (aka the thrust) on a current carrying wire depends on the direction of the current and the direction of the magnetic field
  • All three will be perpendicular to each other
    • This means that sometimes the force could be into and out of the page (in 3D)

  • The direction of the force (or thrust) can be worked out by using Fleming's left-hand rule:

Flemings Left Hand Rule, downloadable IGCSE & GCSE Physics revision notes

Fleming’s Left-Hand Rule can be used to determine directions of the force, magnetic field and current

Worked example

Use Fleming’s left-hand rule to show that if the current-carrying wire is placed into the magnetic field between the poles of the magnet, as shown below, there will be a downwards force acting on the wireWE Flemings LHR Question Image, downloadable IGCSE & GCSE Physics revision notes

Step 1: Determine the direction of the magnetic field

    • Start by pointing your First Finger in the direction of the (magnetic) Field.

Step 2: Determine the direction of the current

    • Now rotate your hand around the first finger so that the seCond finger points in the direction of the Current

Step 3: Determine the direction of the force

    • The THumb will now be pointing in the direction of the THrust (the force)
    • Therefore, this will be the direction in which the wire will move

WE Flemings LHR Answer Image, downloadable IGCSE & GCSE Physics revision notes

Examiner Tip

Remember that the magnetic field is always in the direction from North to South and current is always in the direction of a positive terminal to a negative terminal.Feel free to use Fleming's left hand rule in your exam, just don't make it too obvious or distracting for other students!

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Ashika

Author: Ashika

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Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.