Fleming's Right-Hand Rule

Author: E.E. Kimberly

By a rule known as Fleming's right-hand rule, the direction of the emf generated in a moving conductor may be found if the direction of the magnetic field and the direction of motion of the conductor in the field are known. The rule is as follows: Extend the thumb, the first finger, and the second finger of the right hand mutually at right angles along the axes of an imaginary three-plane coordinate system. Point the thumb in the direction of motion of the conductor relative to the field, and point the forefinger in the direction of the flux (magnetic lines), as indicated in Fig. 1-4. The second finger will then point along the conductor in the direction of the positive end of the conductor.

Fig. 1-4. Fleming's Rule of Generated emf

If the conductor of Fig. 1-4 were a part of a complete circuit, the current which the electromotive force would cause to flow would be said by convention to flow from the positive end of the conductor. All rules of current flow are based on that premise, regardless of the fact that it is now known that the electrons actually flow in the opposite direction. It is not necessary to modify that point of view until the actual direction of electron flow must be considered in electron tubes.