Cho mạch điện như hình vẽ u = 12V r1 = 20 ôm, R2 = 5 ôm, r3 = 8 ôm, có một vôn kế v có điện trở rất lớn và một Ampe kế có điện trở rất bé a) Tìm số chỉ vôn kế khi nó mắc giữa A và N trong hai trường hợp K mở và K đóng.

b) Thay vôn kế bằng ampe kế. Hỏi những câu a

Apoint charge +q is at the origin. a spherical gaussian surface centered at the origin encloses +q. so does a cubical surface centered at the origin and with edges parallel to the axes. select "true" or "false" for each statement below. the electric flux through the spherical surface is greater than that through the cubical surface. suppose (for this statement only), that q is moved from the origin but is still within both the surfaces. the flux through both surfaces remains unchanged. the area vector and the e-field vector point in the same direction for all points on the spherical surface. the e-field at all points on the spherical surface is equal due to spherical symmetry. the flux through the spherical gaussian surface is independent of its radius.