15 Two solenoids have the same crosssectional area and lengt

15

Two solenoids have the same cross-sectional area and length, but the first one has twice as many turns per unit length as the second. The ratio of the self-Inductance of the second solenoid to that of the first is 1: 1 1: 2 1: 4 2: 1 4: 1

Solution

Self inductance of a solenoid is directly proportional to the sqaur of number of turns per unit length.

So for solenoids of same cross-section area and length

L1/L2 = (N1/N2)²

N1=2N2

So L2:L1 = 1:4