Final answer:
When the current in a solenoid increases, the induced emf acts to decrease the magnetic flux by Lenz's Law, in an attempt to oppose the change in flux caused by the increased current.
Step-by-step explanation:
If the current increases in a solenoid, the induced emf acts to decrease the flux. This is due to Lenz's Law, which states that the direction of the induced emf and the resulting current will be such as to oppose the change in magnetic flux that produced them. Therefore, when the current through a solenoid increases, it leads to an increase in the magnetic field and magnetic flux. The induced emf will generate a current that creates a magnetic field in the opposite direction, effectively attempting to decrease the magnetic flux back to its original state. This is how the induced emf maintains the overall stability of the magnetic flux within the solenoid.
It's also important to note that the induced EMF is related to the physical geometry of the device and the rate of change of current. While the number of coils in a solenoid and the rate at which the current changes are both important factors in determining the magnitude of the induced emf, the relationship involves the total change in magnetic flux through the solenoid, which is proportional to the number of turns (coils) in the solenoid.