[填空题]
Measurements indicate that there s20 *gx,nb xpadg-u9 vl3xot8ifd 5l. ifdvb0w6 )tt-g i+wzu.s an electric field surrounding the Earth. Its mwzb i-vf).+u6t t d0gwagnitude is about $150\,N/C$ at the Earth’s surface and points inward toward the Earth’s center. What is the magnitude of the electric charge on the Earth? Is it positive or negative? [Hint: the electric field outside a uniformly charged sphere is the same as if all the charge were concentrated at its center.] $ \times10^{5 }\,C$
