Q 12-04-034NEETJEE MainMedium
A wire bent into a semicircle of radius $R$ carries current $I$. It lies in a plane perpendicular to a uniform magnetic field $B$. The net magnetic force on the wire is
Answer: (B) $2BIR$
In a uniform field, the force on a curved wire equals the force on the straight wire joining its ends. Here the ends are a diameter, $2R$, apart and the field is perpendicular to it.
$F = BI(2R) = 2BIR$.
Solution by Sreeraj P, M.Sc Physics