A long straight wire of a circular cross-section of radius 'a' carries a steady current I. The current is uniformly distributed across the cross-section. Apply Ampere's circuital law to calculate the magnetic field at a point at distance 'r' in the region for (i) `rlta` and (ii) `rgta`.

Explanation

To solve the problem of finding the magnetic field at a distance 'r' from a long straight wire carrying a steady current 'I', we will apply Ampere's circuital law in two cases: when \( r < a \) (inside the wire) and when \( r > a \) (outside the wire).

### Step-by-Step Solution:

**Step 1: Understanding Ampere's Circuital Law**
- Ampere's circuital law states that:
\[
\oint \mathbf{B} \cdot d\mathbf{l} = \mu_0 I_{\text{enc}}
...