A coil of $12$ turns made by a constant length current carrying wire. If number of turns makes $3$ then change in magnetic field produced at its centre
A$6.25\%$ decreases
B$93.75\%$ decreases
C$6.25\%$ increases
D$93.75\%$ increases
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B$93.75\%$ decreases
b $\mathrm{B} \propto \mathrm{N}^{2} \Rightarrow \frac{\mathrm{B}_{2}}{\mathrm{B}_{1}}=\left(\frac{\mathrm{N}_{2}}{\mathrm{N}_{1}}\right)^{2}=\left(\frac{3}{12}\right)^{2}=\frac{9}{144}$
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