A long straight wire carries a current of $5\text{A}$. Find the magnetic field at a point $2\text{cm}$ from the wire. Take ${\mu }_0=4\pi \times 10^{-7}\text{T⋅m/A}$.

Step-by-step solution

1. Write the expression for magnetic field due to a long straight conductor: $B=\frac{{\mu }_{0}I}{2\pi r}$.
2. Convert the distance to metres: $r=2\text{cm}=0.02\text{m}$.
3. Substitute the given values: $B=\frac{4\pi \times 10^{-7}\times 5}{2\pi \times 0.02}$.
4. Simplify the expression: $B=\frac{20\pi \times 10^{-7}}{0.04\pi }=\frac{20\times 10^{-7}}{0.04}=5\times 10^{-5}\text{T}$.
5. State the result.

Concept tested: Magnetic field of a straight conductor

Published 23 August 2026 · How this solution was prepared and checked

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