21.53. Positive electric charge is distributed along the y-axis with charge per unit length A. (a) Consider the case where charge is distributed only between the points y = a and y = 0. For points on the +x-axis, graph the x-component of the electric field as a function of x for values of x between x = a/2 and x = a. (b) Consider instead the case where charge is distributed along the entire y-axis with the same charge per unit length A. Using the same graph as in part (a), plot the x-component of the electric field as a function of x for values of x between -2a and x = 4. Label which graph refers to which situation.
21.60. Sketch the electric field lines for a disk of radius R with a positive uniform surface charge density σ. Use what you know about the electric field very close to the disk and very far from the disk to make your sketch.
21.63. Point charges q1 = -4.5 nC and q2 = +45 nC are separated by 3.1 m, forming an electric dipole. (a) Find the electric dipole moment (magnitude and direction). (b) The charges are in a uniform electric field whose direction makes an angle of 36.98° with the line connecting the charges. What is the magnitude of this field if the torque exerted on the dipole has a magnitude of 7.2 x 10^-9 Nm?