COMEDK2019PhysicsMagnetic Effects of Current
Three long straight wires A, B and C are carrying currents as shown in figure. Then, the resultant force on B is directed
Options
- Atowards A
- Btowards C
- Cperpendicular to the plane of paper and outward
- Dperpendicular to the plane of paper and inward
Correct answer
B. towards C
Step-by-step solution
Magnetic field at any point due to a straight current carrying wire is given by B= ₀ I 2 d where, d is the distance of the point from the wire and I₁ is current flowing in the wire. Force due to this magnetic field on current carrying wire is given by F=B I L where, L is the length of the wire. Force on wire B due to wire A, F_ A =B I L F_ A = ₀ 1 2 d 2 L Force on wire B due to wire C, F_ C =B I L F_ C = ₀ 3 2 d 2 L It is clear that F_ C >F_ A . Hence, net force is towards wire C .