JEE Advanced2006PhysicsMagnetic Effects of CurrentActual
Which of the following statement is correct in Infinitely long wire kept perpendicular to the paper carrying current inwards the given figure?
Options
- Anet force on the loop is zero
- Bnet torque on the loop is zero
- Cloop will rotate clockwise about axis OO ^ when seen from O
- Dloop will rotate anti-clockwise about OO ^ when seen from O
Correct answer
A. net force on the loop is zero
Step-by-step solution
F _ B A =0 , because magnetic lines are parallel to this wire. F _ C D =0 , because magnetic lines are antiparallel to this wire. F _ C B is perpendicular to paper inwards and F _ A D is perpendicular to paper outwards. These two forces (although calculated by integration) cancel each other but produce a torque which tend to rotate the loop in clockwise direction about an axis O O^ .