Question

A straight wire of diameter 0.5 mm carrying a current 2 A is replaced by another wire of diameter 1 mm carrying the same current.The strength of magnetic field at a distance 2 m away from the centre is

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

Answer 1

The correct option is C unchanged

$B=\frac{{\mu }_o}{2\pi }\frac{i}{r}$,independent of diameter of wire.

The magnetic field outside the conducting wire is independent of diameter of wire, hence it will remain unchanged.