Top Qs
Timeline
Chat
Perspective
FBI mnemonics
From Wikipedia, the free encyclopedia
Remove ads
The various FBI mnemonics (for electric motors) show the direction of the force on a conductor carrying a current in a magnetic field as predicted by Fleming's left hand rule for motors[1] and Faraday's law of induction.
This article needs additional citations for verification. (February 2024) |


Other mnemonics exist that use a right hand rule for predicting resulting motion from a preexisting current and field.
Remove ads
Configuration, using the left hand
'FBI'
The left hand is held with the thumb, first finger and second finger mutually at right angles.
Configuration, using the right hand
Other sources use the right hand to predict force, though the fingers used vary:
'FIB'
- Thumb = F ("thrust")
- Index finger = I or V
- Middle finger ("Birdie") = B
'IBF'

In this alternative, some versions recommend not extending the middle finger, but instead imagining the force coming from the palm of the hand.
- Thumb = I or V
- Index finger = B
- Middle finger = F
Other frequently confused rules
Prediction of direction of field ('B')

The rules above are usually used to predict 'F' based upon 'B' and 'I' - the force on a moving charge when moving through a field, whether or not the charge is carried in a wire. However, this rule should not be confused with a different right hand grip rule for the prediction of the direction of a field ('B') produced by current ('I') traveling through a wire.
Symmetry
Remove ads
References
External links
Wikiwand - on
Seamless Wikipedia browsing. On steroids.
Remove ads