Fleming’s left-hand rule for motors – wikipedia electricity and magnetism purcell pdf


In an electric motor, the electric current and magnetic field exist (which are the causes), and they lead to the force that creates the motion (which is the effect), and so the left hand rule is used. In an electric generator, the motion and magnetic electricity lessons 4th grade field exist (causes), and they lead to the creation of the electric current (effect), and so the right hand rule is used.

To illustrate why, consider that many types of electric motors can also be used as electric generators. A vehicle powered by such a motor can be accelerated up to high speed by connecting the motor to a fully charged battery. If the motor is then disconnected from the fully charged battery, and connected instead to a completely flat battery, the vehicle will decelerate. The motor will power kinetic energy act as a generator and convert the vehicle’s kinetic energy back to electrical energy, which is then stored in the battery gas dryer vs electric dryer safety. Since neither the direction of motion nor the direction of the magnetic field (inside the motor/generator) has changed, the direction of the electric current in the motor/generator has reversed. This follows from the second law of thermodynamics (the generator current must oppose the motor current, and the stronger current outweighs the other to allow the energy to flow from the more energetic gas station in spanish source to the less energetic source).

The direction of the induced magnetic field is sometimes remembered by Maxwell’s corkscrew rule. That is, if the conventional current is flowing away from the viewer, the magnetic field runs clockwise round the conductor, in the same direction that a corkscrew would have to turn in order to move away from the viewer. The direction of the induced magnetic field is also sometimes remembered by the right-hand grip rule, as depicted in the i feel electricity in my body illustration, with the thumb showing the direction of the conventional current, and the fingers showing the direction of the magnetic field. The existence of this magnetic field can be confirmed by placing magnetic compasses at various points round the periphery of an electrical conductor that is carrying a relatively large electric current.

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 gas approximation; 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 c gastronomie traiteur avis 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 m gasbuddy 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 k gas oroville 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 electricity sources usa, and for this switching to be continued indefinitely.)