Educator

Motional EMF

• When a conducting rod of length L moves with speed v in a magnetic field B that is perpendicular to both the rod and the direction of motion, an emf is induced across the rod. This emf, known as motional emf, is given by BLv.
• If a rod, of length L, rotates with angular velocity w about a pivot at one end of the rod, and if a magnetic field exists in space, perpendicular to plane of rotation, an emf will be induced in the rod; it is given by (1/2)wBL^2.
• Examples are provided in the lecture that show how to calculate the force that an external agent must exert in order to pull a rod on rails at constant speed in the presence of a magnetic field, and in the absence of this force, how the speed of the rod decreases with time.