One metre length of wire carries a constant current. The wire is bent to form a circular loop. The magnetic field at the centre of this loop is $B$. The same is now bent to form a circular loop of smaller radius to have four turns in the loop. The magnetic field at the centre of this new loop is
A$4 B$
B$16 B$
C$B/2$
D$B/4$
Medium
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B$16 B$
b (b) $B' = {n^2}B \Rightarrow B' = {(4)^2}B = B' = 16B$
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