Question

Calculate the value of magnetic field at a distance of 3 cm from a very long, straight wire carrying a current of 6A.

Hint:

Magnetic field decreases inversely with distance from a wire; use Ampère’s law for straight conductors.

Answer 1

Magnetic field due to a long straight wire:
\[ B = \frac{\mu_0 I}{2 \pi r}, \] where \( \mu_0 = 4 \pi \times 10^{-7} \, \text{T m/A} \), \( I = 6 \, \text{A} \), \( r = 3 \, \text{cm} = 0.03 \, \text{m} \).
\[ B = \frac{4 \pi \times 10^{-7} \times 6}{2 \pi \times 0.03} = \frac{24 \pi \times 10^{-7}}{0.06 \pi} = \frac{24 \times 10^{-7}}{0.06} = 4 \times 10^{-5} \, \text{T}. \] Answer: \( 4 \times 10^{-5} \, \text{T} \).