FBI mnemonics
# FBI mnemonics

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 and Faraday's law of induction.

Other mnemonics exist that use a right hand rule for predicting resulting motion from a preexisting current and field.

## Configuration, using the left hand

### 'FBI'

The left hand is held with the thumb, first finger and second finger mutually at right angles.

* The Thumb represents F - Thrust (or resulting Motion).
* The First finger represents B - Field.
* The Second finger represents I or V - Current (in the classical direction, from positive to negative).

## 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

| 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 |
