Three long straight wires carrying current are arranged mutually parallel as shown in the figure. The force experienced by 15 cm length of wire Q i $s _____.$
(μ₀ = 4π × 10⁻⁷ T·m/A)

Question

Three long straight wires carrying current are arranged mutually parallel as shown in the figure. The force experienced by 15 cm length of wire Q i s _____. (μ₀ = 4π × 10⁻⁷ T·m/A)

G1 Physics · Accepted Answer

Wire P carries 3 A upward. Wire Q carries 1 A downward. Wire R carries 2 A downward. Distances are PQ = 3 cm = 0.03 m, QR = 2 cm = 0.02 m. The force per unit length between two long parallel wires is F/l = μ₀I₁I₂/(2πd). P and Q carry currents in opposite directions, so they repel. Therefore the force on Q due to P is toward R. Q and R carry currents in the same direction, so they attract. Therefore the force on Q due to R is also toward R. Hence the two forces add: F(net) = [μ₀/(2π)] I(Q) l [I(…