A circular wire loop carrying a current I in the anti-clock wise sense is placed in a uniform magnetic field B directed into the plane of the coil as shown in figure.  The loop will tend to:

 

Since to loop carries a current, a charge (say q) moves along the circle with a velocity (say v). The velocity v is tangential to the circle at every point. The direction of v gives the direction of the current as shown in figure

From Fleming's left hand rule, the direction of the force F exerted by magnetic field is radially inwards towards O at every point. Hence the loop tends to contract. Furthermore, since F is perpendicular to v, the force does no work on the loop. Hence it cannot have any translatory motion.