Question

MAGNETISM

Answer 1

Why not D ?

Answer 2

D contradicts Newton's third law of motion: bodies in interaction must exert exactly opposite forces on each other.

Answer 3

consider this--
here force on wire 2 is
\[F_{21}=\frac{ \mu _0I_1I_2 }{ 2 \pi d }\\d=distence~ Between~ the~wires\\\]
and force on wire 1 will be the same that of wire 2 but opposite in direction.
so\[force~on~wire1=F_{12}=\frac{ \mu _0I_2I_1 }{ 2 \pi d }\]
so in your problem
\[I_1=1~amp~ and~I_2=2~amp\\so ~force~on~wire~2 =F_{21}=\frac{ \mu _0*2* 1}{ 2 \pi d }\\and~force~on~wire~1 ~is=F_{12}=\frac{ \mu_0*1*2 }{ 2 \pi d}\\so~ F_{12}=F_{21}\\so ~they~are~same~In~magnitude~and~opposite~In~direction\]
thats why opt(C) is correct