A straight current-carrying wire produces a magnetic field around it. The magnetic field strength (B) at a point near the wire can be calculated using the formula:

B = (μ₀ * I) / (2π * r)

Where B is the magnetic field strength, μ₀ is the permeability of free space (constant value of 4π × 10^-7 Tm/A), I is the current flowing through the wire, and r is the distance from the wire to the point. The direction of the magnetic field can be determined using the right-hand rule.

The right-hand rule states that if you align your thumb in the direction of the current, then the curled fingers will point in the direction of the magnetic field loops.

Let's take an example to understand this concept better. Imagine a straight wire carrying a current of 2 Amperes. If we measure the magnetic field at a distance of 5 centimeters from the wire, we can calculate it as follows:

B = (4π × 10^-7 Tm/A * 2 A) / (2π * 0.05 m) = 0.002 T

This means that at the specified distance, the magnetic field strength is 0.002 Tesla. The direction of the magnetic field can be found using the right-hand rule.