A long, straight wire carrying a current of 30 A is placed in an external uniform magnetic field of `4.0 xx 10^-4` T exists from south to north. Find at a point 2.0 away from the wire.

Explanation

To solve the problem, we need to find the resultant magnetic field at a point 2.0 cm away from a long straight wire carrying a current of 30 A, placed in an external uniform magnetic field of \(4.0 \times 10^{-4}\) T directed from south to north.

### Step-by-Step Solution:

1. **Identify the Given Values:**
- Current, \(I = 30 \, \text{A}\)
- External magnetic field, \(B_{\text{ext}} = 4.0 \times 10^{-4} \, \text{T}\) (directed from south to north)
- Distance from the wire, \(d = 2.0 \, \text{cm} = 0.02 \, \text{m}\)
...