1 \begin{problem*}{31.30}
2 A rectangular coil with resistance $R$ has $N$ turns, each of length
3 $l$ and width $w$ as shown in Figure~P31.30. The coil moves into a
4 uniform magnetic fiield $\vect{B}$ with constant velocity $\vect{v}$.
5 What are the magnitude and direction of the total magnetic force on
6 the coil \Part{a} as it enters the magnetic field, \Part{b} as it
7 moves within the field, and \Part{c} as it leaves the field?
22 Vector B = BField(phi=-90);
23 vector_field((l/2 + 7mm + u/2, 0), width=u, height=u, v=B, outline=dashed);
24 Vector v = Velocity((l/2, 0), "$\vect{v}$"); v.draw();
25 path p = scale(l, w)*shift((-0.5, -0.5))*unitsquare;
27 draw(shift(1.5pt*dir(-45))*p);
28 Distance Dl = Distance((-l/2, -w/2), (l/2, -w/2), "$l$", offset=6pt);
30 Distance Dw = Distance((-l/2, w/2), (-l/2, -w/2), Label("$w$", embed=Shift),