Describe The Emf Induced By Motion ?
Whenever a change q moves in a magnetic field, the charge experiences a force F the magnitude of which given by F = quB sinθ = q/t lB sinθ In vector form the force is given by F = qv × B = q/t l × B The force on the charge +q is at right angles to v and B. in the example illustrated in the force on a positive charge would be upward. A moving charge constitutes a current. The force on a charge in motion is that on the equivalent conventional current. The vectors representingv, B and F are mutually perpendicular. If the charge is free to respond to this force, it will move in the direction of F. An electric conductor, such as a copper wire, has free electrons in it. Consider a wire moving across a magnetic field. The component B sin θ perpendicular to the velocity will exert a force on charge in the wire along the direction of the wire. Positive charges in the wire would experience a force directed toward b; electrons experience a force in the opposite direction, and the free electrons accumulate at a leaving a deficiency of electrons at b. Equation gives F/q = vB sin θ. Thus an electric field is set up in the conductor directed from a towards b, with a magnitude E = F/q = vB sinθ. The emf e induced in the wire of length l is e = W/q = Fl/q = Eql/q = lvB sin θ When B is expressed in webers per square meter, l in meters, and v in meters per second, the emf is in joules per coulomb, or volts. The emf exists whether or not there is a complete circuit for current. If the moving conductor slides along stationary conducting rails a current will be establishes in the sense shown.
