Question

Find the magnetic field at a point 5 cm away from a long straight wire carrying current \( I = 20\,A \).

Hint:

Always convert distance to meters. The magnetic field due to a long wire is inversely proportional to the distance from it.

Answer 1

Use the Ampere’s Law formula: \[ B = \frac{\mu_0 I}{2\pi r} \] Where: \[ \mu_0 = 4\pi \times 10^{-7} \, Tm/A, \quad I = 20\,A, \quad r = 0.05\,m \] \[ B = \frac{4\pi \times 10^{-7} \cdot 20}{2\pi \cdot 0.05} = \frac{8 \times 10^{-6}}{0.05} = 1.6 \times 10^{-4} \, T \] Final Answer: \[ \boxed{B = 1.6 \times 10^{-4} \, \text{T (Tesla)}} \]