question_answer

A rectangular loop carrying a current T is situated near a long straight wire, such that the wire is parallel to one of the sides of the loop and is in the plane of the loop. If steady current I is established in the wire as shown in the figure, the loop will:

A)  rotate about an axis parallel to wire.

B)  move away from the wire

C)  move towards the wire

D)  remain stationary

Correct Answer: C

Solution :

A non uniform magnetic field will be produced to the right of straight wire\[{{\vec{F}}_{PS}}\,=-{{\vec{F}}_{QR}}\] Force on wire PQ will be  towards straight wire carrying current. Force on wire RS will be away from straight wire carrying current. Wire PQ is nearer to the current carrying wire and hence force on it will be more. So, Loop will move towards wire.