An annular wire loop ABCD carries a current $I_{1}$ as shown in figure. O is the common centre of the curved parts AB and CD of the loop. A straight wire passing through O and perpendicular to the plane of the loop carries a current $I_{2}$ directed towards the reader. Then

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The net torque on the loop is zero

The net force on the loop is zero

As seen from O the loop will rotate in clock wise sense about axis OP

As seen from O the loop will rotate in anticlockwise sense about axis OP

answer is A, C.

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Detailed Solution

The magnetic field B due to current $I_{2}$ is tangential to the curved parts AB and CD of the loop. Hence every current element dl of parts AB and CD is parallel or antiparallel to B. The magnetic force on AB or CD is zero since $θ = 0 ° o r 180 °$ in the expression $d F = B I d l \sin θ$ . The magnetic force on straight parts AD and BC is not zero. The magnetic force on AD is directed towards the reader which is equal and opposite to the force on BC which is directed away from the reader. These equal and opposite forces cancel each other. Therefore, the net force on the loop ABCD is zero. Since these equal and opposite forces do not act at the same point, they will exert a net torque on the loop which will rotate it in the clockwise sense when viewed from O.