What is the direction of E̅(vector) just outside the surface of such a sphere?

(a) Tangent to the surface of the sphere;

(b) Perpendicular to the surface, pointing toward the sphere;

(c) Perpendicular to the surface, pointing away from the sphere;

(d) There is no electric field just outside the surface.

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 E̅(vector) 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.