Three long, straight and parallel wires are arranged as shown in figure. The force experienced by 10 cm length of wire Q is

F=μ0i1i2l2πa-μ0i3i2l2πb =4π×10-7×20×10×10×10-22π×2×10-2-4π×10-7×10×30×10×10-22π×10×10-2 =4π×10-7×10×10-22π×10-2[100-30] =20×10-7×70=1400×10-7 =1.4×10-4 N toward right.