Answer:
Step-by-step explanation:
Length of both the solenoids = l
Area of crossection of both the solenoids = A
Current in both the solenoids = i
Let the number of turns in coil A is 4N and the number of turns in coil B is N.
The self inductance due to the long solenoid is given by

As the current, area of crossection and the length is same so


So, LA : LB = 16 : 1