The magnetic field at a distance r from a long wire carrying current I is 0.4 T. The magnetic field at a distance 2r from the wire is
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 0.2 T
Given:
Magnetic field at distance r from a long straight current-carrying wire is 0.4 T.
Formula: Magnetic field due to a long straight wire is given by:
$B = \frac{\mu_0 I}{2\pi r}$
This implies $B \propto \frac{1}{r}$.
So, if distance is doubled ($r \rightarrow 2r$), then magnetic field becomes:
$B' = \frac{0.4}{2} = 0.2\ \text{T}$