If two coils are very tightly would one over the other, will M increase or decrease as compared to the case when the coils are placed some distance apart?

Explanation

To solve the question regarding the mutual inductance (M) of two coils when they are placed tightly wound one over the other compared to when they are placed some distance apart, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Mutual Inductance**:
- Mutual inductance (M) is a measure of how much the magnetic field generated by one coil induces an electromotive force (EMF) in another coil. It is directly proportional to the magnetic flux linking the second coil due to the current in the first coil.

2. **Initial Condition**:
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