The rectangular loop of wire shown in Fig. $\mathrm { P } 27.77$
has a mass of 0.15$\mathrm { g }$ per centimeter of length and is pivoted
about side ab on a frictionless axis. The current in the wire is
8.2$\mathrm { A }$ in the direction shown.
Find the magnitude and direction
of the magnetic field parallel to
the $y$ -axis that will cause the
loop to swing up until cause the
makes an angle of $30.0 ^ { \circ }$ with the
yz-plane.