Question

Three long straight wires $A, B$ and $C$ are carrying currents as shown in figure. Then the resultant force on $B$ is directed .............

• A. towards A
• B. towards C
• C. perpendicular to the plane of paper and outward
• D. perpendicular to the plane of paper and inward

Answer 1

Answer: (B)

towards C

Answer 2

B has attractive force due to A and C both $\therefore$ $F_{AB} = \frac{\mu_0}{4 \pi } \frac{2 \times 1 \times 2}{d} = \frac{4 \pi_0}{4 \pi d}$ and $F_{CB} = \frac{\mu_0}{4 \pi } \frac{2 \times 2 \times 3}{d} = \frac{12 \,\mu_0}{4 \pi d}$ Clearly $F_{CB}$ is more effective.