COMEDK2013PhysicsMagnetic 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
- Aperpendicular to the plane of paper and outward
- Bperpendicular to the plane of paper and inward
- Ctowards A
- Dtowards C
Correct answer
D. towards C
Step-by-step solution
The magnetic force between two current carrying wires for current in same direction is attractive. Thus, force on B due to the magnetic field produced due to wire A is aligned F_ A &=B_ A I_ B l= ₀ I_ A 2 d I_ B l &= ₀ 1 2 l 2 d = 2 ₀ l 2 d , towards A ( i ) aligned Similarly, force due to field of wire C , aligned & F_ C =B_ C I_ B l= ₀ I_ C I_ B l 2 d = ₀ 3 2 l 2 d & F_ C = 6 ₀ l 2 d , towards C aligned From Eqs. (i) and (ii) we get F_ C >F_ A The resultant force on B is directed towards C .