Question

A wire of $6.28 \,m$ length is converted into two semicircular loops of same radius as shown in the figure. Then the magnitude of magnetic force (in newton) on the wire will be

Answer 1

$\left|\vec{F}_{m}\right| =B I|\vec{L}| $
$=B I(4 R) (\because 2 \pi R=6.28 \therefore R = 1\,m) $
$=5 \times 1 \times 4 \times 1 $
$=20\, N$