A cylinder of radius `R_(1)` have cylinderical cavity of radius `R_(2)` as shown in the figure and have current density J (down ward). Find Magnetic field when
when point is in cavity

Explanation

To find the magnetic field at a point inside a cylindrical cavity of a cylinder with a uniform current density, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Setup**:
- We have a solid cylinder of radius \( R_1 \) with a cylindrical cavity of radius \( R_2 \).
- The current density \( J \) is directed downwards throughout the cylinder, including the cavity.

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