In Eq. (10.1), the negative sign indicates that if the magnetic flux linking the loop increases, the induced emf produces a
current whose flux opposes the increase in the flux linking the loop and if the flux decreases, the emf produces a current
whose flux augments the flux linking the loop. To see this, consider first the loop in Figure 10.2a. Using the right-hand rule
for the flux generated by current I1 in loop (1), an increase in the current increases the flux through loops (1) and (2). Loop (1)
is then the source of the flux. An emf is generated in loop (2), but, because loop (2) is open, there is no current in the loop and
therefore no induced flux due to loop (2). Now, consider the situation in Figure 10.2b where, again using the right-hand rule,
an increase in the flux due to loop (1) produces a negative emf in loop (2). This corresponds to Faraday’s law. This induced
emf, shown in Figure 10.2c, can be viewed as the source of a flux that is in the opposite direction to the flux in Figure 10.2a.
Thus, the induced emf produces a flux that opposes the flux that generated the emf. This relation between induced
electromotive force and the magnetic flux linkage is defined by Lenz’s law, which states: