Mutual inductance and coefficient of coupling:
The equivalent inductance of two series connected coil (with mutual inductance among them) is 0.8 or 0.2 Henry based on the relative directions of currents in the coil. If self inductance of one coil is 0.4 Henry then find out (a) Mutual inductance; and (b) coefficient of coupling.
Solution
For M-Positive :
L_{eq} = L_{1} + L_{2} + 2M
0.8 = L_{1} + L_{2} + 2M ---------------- (i)
Figure
For M negative
L_{eq} = L_{1} + L_{2} - 2M
0.2 = L_{1} + L_{2} - 2M ----------- (ii)
From Eqs. (i) and (ii)
0.6 = 4M ⇒ M =0.6/ 4 = 0.15 Henry
But L_{1} = 0.4 Henry
∴From Eq. (i)
0.8 = 0.4 + L_{2} + 2 × 0.15
∴ L_{2} = 0.1 Henry
The coefficient of coupling