Fleming's left-hand rule: the mnemonic picture
The left hand should be held as shown below, with the thumb, first finger and second finger all at 90° to each other.
Your first finger should be placed in line with the direction of the magnetic field (i.e. north to south).
The second finger needs to be placed in line with the direction of current in the wire.
The thumb will now show you the direction of the motion on the wire or, in this case, the carbon rod.
Using Fleming's left-hand rule we can predict here that if we turn on the electrical supply the carbon rod will move in the thumb's direction.
See below for the result:
The rod has moved to the right as predicted.
