Find the mutual inductance of two concentric coils of radii `a_(1)` and `a_(2)(a_(1) lt lt a_(2))` if the planes of the coils make an angle `theta` with each other.

Explanation

To find the mutual inductance of two concentric coils of radii \( a_1 \) and \( a_2 \) (where \( a_1 \ll a_2 \)) with their planes making an angle \( \theta \) with each other, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Geometry**:
- We have two coils: a smaller coil with radius \( a_1 \) and a larger coil with radius \( a_2 \).
- The planes of the coils are inclined at an angle \( \theta \) to each other. This means that the area vectors of the coils will also make an angle \( \theta \) with each other.

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