Question

Two coils of self inductance 2 mH and 8 mH are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is

• A. 16 mH
• B. 10 mH
• C. 6 mH
• D. 4 mH

Answer 1

Answer: (D)

4 mH

Answer 2

The correct answer is (D) : 4 mH
By using $M = K \sqrt{ L _{1} L _{2}}$
Here $K =1, \,L _{1}=2 mH,L_2=8mH$
⇒ $M =\sqrt{16}$
$=4 \,mH$