An infinitely long straight wire carries a current of $6.0\text{A}$. Calculate the magnitude of the magnetic field at a point located $15\text{cm}$ from the wire. State the direction of the field using the right‑hand rule.

Step-by-step solution

1. Use the formula for the magnetic field of a long straight wire: $B=\frac{{\mu }_{0}I}{2\pi r}$, where ${\mu }_0=4\pi \times 10^{-7}\text{T⋅m/A}$.
2. Convert the distance to metres: $r=15\text{cm}=0.15\text{m}$.
3. Substitute the values: $B=\frac{4\pi \times 10^{-7}\times 6.0}{2\pi \times 0.15}$.
4. Cancel $\pi$ and simplify: $B=\frac{24\times 10^{-7}}{0.30}=8.0\times 10^{-6}\text{T}$.
5. Apply the right‑hand rule: point the thumb along the direction of current; the field circles the wire. At a point to the right of the wire the field points into the page.

Concept tested: Magnetic field of a straight current‑carrying wire

Published 17 September 2026 · How this solution was prepared and checked