The magnetic field B, at all points within a circular region of radius R, is uniform in space and directed into the plane of the page as shown in Fig. 29.54. (The region could be a cross section inside the windings of a long, straight solenoid.) If the magnetic field is increasing at a rate dB/dt, what are the magnitude and direction of the force on a stationary positive point charge q located at points a, b, and c? (point a is a distance r above the center of the region, point b is a distance r to the right of the center, and point c is at the center of theregion.)

* B x x x xRx T-b*