a
(a) Force on wire \(Q\) due to wire \(P\) is
\({F_P} = {10^{ - 7}} \times \frac{{2 \times 30 \times 10}}{{0.1}} \times 0.1\)\( = 6 \times {10^{ - 5}}\,N\) (Towards left)
Force on wire \(Q\) due to wire \(R\) is
\({F_R} = {10^{ - 7}} \times \frac{{2 \times 20 \times 10}}{{0.02}} \times 0.1 = 20 \times {10^{ - 5}}\,N\) (Towards right)
Hence \({F_{net}} = {F_R} - {F_P} = 14 \times {10^{ - 5}}N = 1.4 \times {10^{ - 4}}\,N\)
(Towards right)