28. The field outside a toroid is zero because: (a) The net current flowing through its surface is zero because there is no current outside the toroid. (b) The net current flowing across its surface is zero because an equal number of currents cross in both directions. (c) The net current flowing through its surface is zero because the magnetic field decreases as it moves away from the toroid. (d) The net current outside is zero because the magnetic field decreases as it moves away from the toroid. 29. In a coaxial cable, the inductance per unit length depends on: (a) A variation in the ratio of outer radius over inner radius. (b) The insulating material between the inner and outer radius. (c) A variation in cable length. (d) A variation in the ratio of inner radius over outer radius. 30. In a solenoid B is: (a) At its terminals, half the magnitude it had at its center. (b) Maximum in its terminals. (c) At the terminals, double the magnitude of the solenoid center. (d) Same throughout the solenoid. 31. Make a graph to represent the following relationship of magnetostatic boundary conditions: n x (92 2 - 961) = $, 32. Make a graph to represent the following relationship of magnetostatic boundary conditions: i . (982 - 981) =9ms 33. Wavelength is the distance between: (a) A maximum and a minimum. (b) Two successive points of the same phase. (c) Two successive highs. (d) The starting time until the first period. 34. The basis vectors change their orientation in: (a) The Cartesian coordinate system. (b) The cylindrical coordinate system. (c) The spherical coordinate system. (d) All systems. 35. A point in any of the coordinate systems is the same, however its description varies. Thus for a point located in A(X1 , y1 ,Z1 ) and another in B(x2 ,y2 ,Z2 ) for its unit vectors it is satisfied that: (a) They vary in the Cartesian system; they do not vary in the cylindrical system; they do not vary in the spherical system. (b) They do not vary in the Cartesian system; they vary in the cylindrical system; they vary in the spherical system. (c) They vary in the Cartesian system; they vary in the cylindrical system; they vary in the spherical system. 36. In class we studied that coordinate systems allow us to express the same point with different descriptions. If we wanted to talk about a five- dimensional orthogonal system, this would be: (a) A coordinate system with constant velocity. L (b) A coordinate system with acceleration. (c) A coordinate system with five axes. (d) An orthogonal system with four axes. 37 Indicat