An infinitely long, straight conductor AB is fixed and a current is passed through it. Another movable straight wire CD of finite length and carrying current is held perpendicular to it and released. Neglect weight of the wire

detailed solution

Correct option is C

The magnetic field (produced by AB) at different points of CD are different and gradually decreases as we are moving from end C to end D ,as a result force per unit length on CD gradually decreases as we are moving from end C to end D .Therefore the the resultant force on CD acts at a point which lies to the left of the centre of mass of CD .This resultant force produces a clockwise moment about the centre of mass of CD'. Hence CD will experience force and torque. From Flemming"s left hand rule it can be seen that the force will be upward .