Short Answer 
Mutual inductance occurs when a changing electric current in one coil induces EMF in another nearby coil, with maximum mutual inductance achieved by winding the coils together for optimal magnetic coupling. This configuration enhances flux linkage and supports the validity of both the assertion and the reason for mutual inductance.
Step 1: Understand Mutual Inductance
Mutual inductance refers to the phenomenon where a change in electric current in one coil induces an electromotive force (EMF) in another coil nearby. This effect is crucial in many electrical applications, such as transformers. The level of mutual inductance is influenced by how the coils are arranged, specifically their proximity and orientation.
Step 2: Importance of Coil Arrangement
The maximum mutual inductance occurs when two coils are wound on each other. This arrangement ensures that the magnetic fields produced by both coils overlap significantly, resulting in greater flux linkage. Key reasons for this include:
- Enhanced magnetic coupling due to close physical proximity.
- Optimal configuration for magnetic field interaction between coils.
- Maximized flux linkage, which directly correlates with the strength of mutual inductance.
Step 3: Conclusion on Assertion and Reason
Both the assertion that maximum mutual inductance occurs when coils are wound together and the supporting reason are true. The efficient magnetic coupling from this arrangement allows for the complete magnetic field generated by one coil to effectively pass through the other. Therefore, the correct conclusion is that both the assertion and reason are valid and interrelated.