The Left-Hand Rule (Magnetic Effect)

Oersted's experiment has been interpreted to mean that "around every wire carrying an electric current there is a magnetic field." The direction of this field at every point, like that around a bar magnet, can be mapped by means of a small compass or by iron filings. If a wire is mounted vertically through a hole in a plate of glass or other suitable nonconductor, and then iron filings are sprinkled on the plate, there will be a lining-up of the filings parallel to the magnetic field. The result shows that the magnetic lines of force or "lines of induction" are concentric circles whose planes are at right angles to the current. The "left-hand rule" used in electromagnetism can always be relied upon to give the direction of the magnetic field due to an electron current in a wire. Derived from experiment, the rule states: "if the current-carrying wire were to be grasped in the left hand, the thumb pointing in the direction of the electron current, negative (-) to positive (+), the fingers will point in the direction of the magnetic induction."