Figure 21.41 shows some of the electric field lines due to three point charges arranged along the vertical axis. All three charges have the same magnitude.
(a) What are the signs of the three charges? Explain your reasoning.
(b) At what point(s) is the magnitude of the electric field the smallest? Explain your reasoning. Explain how the fields produced by each individual point charge combine to give a small net field at this point or points.