Chapter 17, Problem 79PP

Space radiation shielding. One of the hazards facing humans in space is space radiation: high-energy charged particles emitted by the sun. During a solar flare, the intensity of this radiation can reach lethal levels. One proposed method of protection for astronauts on the surface of the moon or Mars is an array of large, electrically charged spheres placed high above areas where people live and work. The spheres would produce a strong electric field $\stackrel{\to }{E}$ to deflect the charged particles that make up space radiation. The spheres would be similar in construction to a Mylar balloon, with a thin, electrically conducting layer on the outside surface on which a net positive or negative charge would be placed. A typical sphere might be 5 m in diameter.

79. Suppose that to repel electrons in the radiation from a solar flare, each sphere must produce an electric field $\stackrel{\to }{E}$ of magnitude 1 × 10⁶ N/C at 25 m from the center of the sphere. What net charge on each sphere is needed?

1. A.    −0.07 C
2. B.     −8 mC
3. C.     −80 µC
4. D.    −1 x 10⁻²⁰ C