Let us suppose the earth (radius 6400 km) had a net charge equivalent to one electron n/m2 of its surface area. Its potential in volt will be
0.12
-0.12
+1.2
-1.2
V=14πε0×QR=14πε0×4πR2eR=14πε0×4πRe=9×1094×227×6⋅4×106−1⋅6×10−19=−0.12 volt.