John Ambrose Fleming introduced two rules to determine the direction of motion (in motors) or the direction of induced current (in generators). The rules are called as Fleming's left hand rule (for motors) and Fleming's right hand rule (for generators).
Fleming's left hand rule
How to remember Fleming's left hand rule?Method 1: Relate the thumb with thrust, fore finger with field and center-finger with current as explained below.
- The Thumb represents the direction of Thrust on the conductor (force on the conductor).
- The Fore finger represents the direction of the magnetic Field.
- The Center finger (middle finger) the direction of the Current.
Fleming's right hand rule
[NOT to be confused with Maxwell's right-hand grip rule]
Faraday's law of electromagnetic induction, whenever a conductor is forcefully moved in an electromagnetic field, an emf gets induced across the conductor. If the conductor is provided a closed path, then the induced emf causes a current to flow. According to the Fleming's right hand rule, the thumb, fore finger and middle finger of the right hand are stretched to be perpendicular to each other as shown in the illustration at right, and if the thumb represents the direction of the movement of conductor, fore-finger represents direction of the magnetic field, then the middle finger represents direction of the induced current.