Question

A straight wire of diameter $0.5mm$ carrying a current of $1A$ is replaced by another wire of $1mm$ diameter carrying the same current. The strength of magnetic field far away is

• A. twice the earlier value
• B. half of the earlier value
• C. quarter of the earlier value
• D. unchanged

Answer 1

The correct option is D unchanged

magnetic field due to straight wire carrying current $i$ at distance $x$ is given as

$B=\frac{{\mu }_{0}i}{2\pi x}$
so $B$ does not depends on the diameter of wire.
$B$ is unchanged