A long, straight wire carrying a current of 200 A, runs trough a cubical wooden box, entering and leaving through holes in the centres of opposite faces (Fig). The length of each side of the e- box is 20.0 cm. Consider an element dl of the wire 0.100 cm long at the center of the box. Compute the magnitude dB of the magnetic field produced by this element at the points a, b, c, d, and e in Fig. Points a, c, and d are at the centres of the faces of the cube; point b is at the midpoint of one edge; and point e is at a comer. Copy the figure and show the directions and relative magnitudes of the field vectors. (Note: Assume that the length dl is small in comparison to the distances from the current element to the points where the magnetic field is to be calculated.)

b. 200 A 200 A *20.0 cm