Correct Answer - Option 2 : 20 mH
Concept:
Mutual Inductance
When two coils are placed close to each other, a change in current in the first coil produces a change in magnetic flux, which lines not only the coil itself but also the second coil as well. The change in the flux induced voltage in the second coil. The voltage is called induced voltage and the two coils are said to have a mutual inductance.
The coupling coefficient K represents how closely they are coupled.
We have expression
\(M = K\sqrt {{L_1}{L_2}} \)
Where
M = Mutual inductance
L1 = Inductance of coil one
L2 = Inductance of coil two
Calculation:
Given
L1 = 16 mH
L2 = 25 mH
K = 1
\(M = K\sqrt {{L_1} \times {L_2}} = 1\sqrt {16 \times 25} = 20\;H\)
For the maximum value of inductance, the value of K must be equal to 1
