c
(c) Suppose length of each wire is \(l\). \({A_{square}} = {\left( {\frac{l}{4}} \right)^2} = \frac{{{l^2}}}{{16}}\)
\({A_{cirle}} = \pi {r^2} = \pi {\left( {\frac{l}{{2\pi }}} \right)^2} = \frac{{{l^2}}}{{4\pi }}\)
Magnetic moment
\(M = iA\)
\( \Rightarrow \frac{{{M_{square}}}}{{{M_{cirde}}}} = \frac{{{A_{square}}}}{{{A_{cirde}}}}\)
\( = \frac{{{l^2}/16}}{{{l^2}/4\pi }}\)\( = \frac{\pi }{4}\)
