It is known that Maxwell's electrodynamicsas usually understood at the present timewhen applied to moving bodies, leads to asymmetries which do not appear to be inherent in the phenomena. Take, for example, the reciprocal electrodynamic action of a magnet and a conductor. The observable phenomenon here depends only on the relative motion of the conductor and the magnet, whereas the customary view draws a sharp distinction between the two cases in which either the one or the other of these bodies is in motion. For if the magnet is in motion and the conductor at rest, there arises in the neighbourhood of the magnet an electric field with a certain definite energy, producing a current at the places where parts of the conductor are situated.
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.
Lecture Slides are screen-captured images of important points in the lecture. Students can download and print out these lecture slide images to do practice problems as well as take notes while watching the lecture.