TABLE OF CONTENTS Heinrich F.E.Lenz was a German scientist who, without knowledge of the work of Faraday and Henry, duplicated many of their discoveries nearly simultaneously. The law which goes by his name, is a useful rule for predicting the direction of an induced current. Lenz s law states that:
Whenever there is a change in the amount of magnetic flux linking an electric circuit, an induced voltage of value directly proportional to the time rate of change of flux linkages is set up tending to produce a current in such a direction as to oppose the change in flux.
To understand Lenz s law, let us consider the transformer shown in Figure 9.3.
Here, we assume that the current in the primary winding has the direction shown and it produces the flux ? in the direction shown in Figure 9.3 by the arrow below the dotted line. Suppose that this flux is decreasing. Then in the secondary winding there will be a voltage induced whose current will be in a direction to increase the flux. In other words, the current produced by the induced voltage will tend to prevent any decrease in flux. Conversely, if the flux produced by the primary winding in increasing, the induced voltage in the secondary will produce a current in a direction which will oppose an increase in flux.
