Q.
A solenoid of length 30cm with 10 turns per centimetre and area of cross-section 40cm2 completely surrounds another co-axial solenoid of same length, area of cross-section 20cm2 with 40 turns per centimetre. The mutual inductance of the system is
Mutual inductance of the system, M=μ0n1n2A2l
where A2 is the area of inner solenoid n1=10cm−1=1000m−1 n2=40cm−1=4000m−1 l=30cm=30×10−2m A2=20cm2=20×10−4m2 ∴M=4π×10−7×1000×4000×20×10−4×30×10−2 =301.44×10−5H=3mH