question_answer

A current \[I\] is flowing in a rectangular loop. It is put close to a wire (long and straight) such that wire is parallel to one of the arms of loop and lies in the plane of loop. If as shown in the figure, a steady current \[I\] flows in the wire, the loop

A)  will rotate about an axis parallel to wire

B)  will move away from the wire

C)  will move towards the wire

D)  will remain steady

Correct Answer: C

Solution :

Force between two current carrying parallel wires \[F=\frac{{{\mu }_{0}}}{4\pi }\,\frac{2{{I}_{1}}{{I}_{2}}l}{r}\]                 If direction of current are same, attractive force will be there or if direction are different, then repulsive force will be there. So, there is attraction between the wire and side AB, whereas there is repulsion between the wire and side CD. \[\therefore \]  \[{{F}_{att}}>{{F}_{rep}}.\] Because AB is more closer to the wire than CD. So, loop will move towards wire.