andré - marie ampère discovered the direction of magnetic field lines.
andré - marie ampère discovered the direction of magnetic field lines.
who discovered the direction of magnetic field lines?
andré - marie ampère
Na
Na
if an external magnetic field is applied horizontally, so that it crosses the flow of electrons (in the wire conductor, or in the electron beam), the two magnetic fields will interact. michael faraday introduced a visual analogy for this, in the form of imaginary magnetic lines of force: those in the conductor form concentric circles round the conductor; those in the externally applied magnetic field run in parallel lines. if those on one side of the conductor are running (from the north to south magnetic pole) in the opposite direction to those surrounding the conductor, they will be deflected so that they pass on the other side the conductor (because magnetic lines of force cannot cross or run contrary to each other). consequently, there will be a large number of magnetic field lines in a small space on that side of the conductor, and a dearth of them on the original side of the conductor. since the magnetic field lines of force are no longer straight lines, but curved to run around the electrical conductor, they are under tension (like stretched elastic bands), with energy bound up in the magnetic field. since this energetic field is now mostly unopposed, its build-up or expulsion in one direction creates — in a manner analogous to newton's third law of motion — a force in the opposite direction. since there is only one moveable object in this system (the electrical conductor) for this force to work upon, the net effect is a physical force working to expel the electrical conductor out of the externally applied magnetic field in the direction opposite to that which the magnetic flux is being redirected to — in this case (motors), if the conductor is carrying conventional current "upwards", and the external magnetic field is moving "away from" the viewer, the physical force will work to push the conductor to the left. this is the reason for torque in an electric motor. (the electric motor is then constructed so that the expulsion of the conductor out of the magnetic field causes it be placed inside the next magnetic field, and for this switching to be continued indefinitely.)
fleming's left-hand rule for motors