Fleming's left hand rule
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Fleming's left hand rule (for electric motors) shows the direction of the thrust on a conductor carrying a current in a magnetic field.
The left hand is held with the thumb, index finger and middle finger mutually at right angles.
- The First finger represents the direction of the Field.
- The Second finger represents the direction of the Current (in the classical direction, from positive to negative).
- The Thumb represents the direction of the Thrust or resultant Motion.
There also exists Fleming's right hand rule (for generators). The appropriately-handed rule can be recalled by remembering that the letter "g" is in "right" and "generator".
Both mnemonics are named after British engineer John Ambrose Fleming who invented them.
Other mnemonics also exist that use a left hand rule or a right hand rule for predicting resulting motion from a pre-existing current and field.
De Graaf's translation of Fleming's left-hand rule - which also uses thrust, field and current - and the right-hand rule, is the FBI rule. The FBI rule changes Thrust into F (Lorentz force), B (direction of the magnetic field) and I (current). The FBI rule is easily remembered by US citizens because of the commonly known abbreviation for the Federal Bureau of Investigation.
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[edit] Right-handed variant
A right-handed variant of this rule is as follows: If the current through a wire is in the direction of the thumb of the right hand, and the direction of an external magnetic field on the wire is represented by the fingers, then the force experienced by the wire will be in the direction the palm of the right hand is facing.
Right-handed variants are useful for people who write with their left hand.
[edit] Symmetry
| Vector | Left-Motor or Right-Generator | Left-Motor or Right-Generator | Left-Motor or Right-Generator | Right-Motor or Left-Generator | Right-Motor or Left-Generator | Right-Motor or Left-Generator |
|---|---|---|---|---|---|---|
| B or Field | First or Index | Thumb | Fingers or Palm | First or Index | Thumb | Fingers or Palm |
| I or Current (+ to - flow) | Fingers or Palm | First or Index | Thumb | Thumb | Fingers or Palm | First or Index |
| Force, Motion, or Thrust | Thumb | Fingers or Palm | First or Index | Fingers or Palm | First or Index | Thumb |
[edit] See also
- Fleming's right hand rule for generators
- Right hand rule
- FBI mnemonics
